SR20DET goes lean on 4k rpm

[VTEC_lol]

So the problem is that my cars wideband shows 17.2 and the car bogs down when accelerating and I hit around 4000rpm. If I keep holding the gas, it'll get fine around 5000rpm and pulls okay till the end.

I have an image I recorded using Nissan DataScan.
Also what is going on with my O2 sensor? That can't be normal?
http://i.imgur.com/IM9Q83b.png

Red arrow shows approx when the car hits a wall and I let go off the gas.

I'm suspecting either vacuum/boost leak or bad o2 sensor?

Mods:

Apexi intake
FMIC
GFB boost controller
3" catback exhaust
Dump valve (recirc)
Walbro 255
Unbranded fuel pressure regulator

Any ideas?


Also on the same topic, I have oil pressure gauge on my dash mounted and it jumps around, most likely bad grounding or wiring? Maybe these two could have a connection?

[VTEC_lol]

bump (also figured out my oil pressure gauge, just had a bad ground wire)

So I thought I would try to pull second and third gear full throttle so I could see something on DataScan and this is what I got:

http://i.imgur.com/jko4wcs.png

So in the first image there are RPM (black), A/F base (blue) and AAC (grey).

So pretty much straight in 4000rpm the car bogs and wideband reads 17.2 for a moment, and if I keep holding the gas, it will get better.

The mess under has pretty much all data in case someone might figure out something.

Please help!

[inopsey]

how old are your fuel pump and filter?

[VTEC_lol]

how old are your fuel pump and filter?

I bought the car a year ago and the previous owner has changed the pump so I really don't know, possibly 2-3 years old.
Fuel filter is pretty old, I ordered a z32 filter so I haven't changed it yet.
Current filter looks like unchanged OEM, I hope it's not since it has been driven for over 210,000+kilometers.

I was thinking the problem is either the filter or maybe clogged injectors? They have been cleaned 2 years ago (by previous owner) so I doubt it but I don't know.

Also the problem kinda began (or when I noticed it) when I poured Redline fuel additive which should clean injectors and fuel system, it also might have clogged my fuel filter maybe?

[inopsey]

definitely change your fuel filter if you have one there already.

[VTEC_lol]

definitely change your fuel filter if you have one there already.
After a long time I finally changed the fuel filter, and absolutely no changes.
Except for now it tends to lean out when I just accelerate (most likely not related to filter), it's about 14,7 and when I slightly give it gas it reads 16.4, 17.2 and sometimes even 20.0.
What is going on? I thought the wideband gauge could have a grounding problem or something but the car clearly hesitates when I accelerate...

E: now that I remember, I tightened my dump valve's spring to almost maximum stiffness, and it may or may not have caused the leaning while driving normally, could a dump valve be behind this?
I need to check if it leaks and maybe loosen the spring

[VTEC_lol]

Alright I changed my o2 sensor which had one broken wire (I found out when I removed it) and replaced it with a new one, and still no changes on the car. It still leans out when I give it a lot of gas.
I'm starting to think the fuel pump might be bad or the wideband is inproperly installed... No smoke is coming out of exhaust so I don't think it does too much damage.... yet

E: Okay so appearantly the car only bogs and leans out when I give it FULL throttle, accelerating with my foot halfway on the pedal makes it run good with no issues, so Im guessing either bad coilpacks, fuel pump or injector spray? Injector resistances are fine but I don't know about the spray.
E2: I was also thinking maybe it's TPS, it's 0.52 at idle and 4.2 at WOT, could that be it?

[VTEC_lol]

Alright well I pulled the coil packs out and found out the first coil is very oxidized and spark plug is also oxidized on the tip, my car isnt misfiring on idle I think and DataScan doesnt see any misfire, but could this be my problem? I tried cleaning it with CRC electronic component cleaner but no changes. This is what it looks like
http://i.imgur.com/CkUVENX.jpg

[inopsey]

your problem is most likely fuel related. you changed the fuel filter but mention that you use a no name fpr. i would suspect that next. put on a oem (ka or sr both fit the oem rail) or another fpr and see if theres a change.

[VTEC_lol]

your problem is most likely fuel related. you changed the fuel filter but mention that you use a no name fpr. i would suspect that next. put on a oem (ka or sr both fit the oem rail) or another fpr and see if theres a change.
I'm thinking it's not the fpr since its adjustment works and is set to 40 PSI and when I'm revving the engine all the way to 6k rpm the pressure remains the same 37-40psi with very little fluctuation, or is that how it's NOT supposed to work?

[inopsey]

thats how its not suppose to work. for turbo you need rising rate regulator, raises fuel psi with boost

[VTEC_lol]

thats how its not suppose to work. for turbo you need rising rate regulator, raises fuel psi with boost
Okay Im prob gonna order a malpassi 384, also I think the problem is indeed the fpr or very leaky injectors, since when I put the car to ACC the fuel pressure rises to about 40psi but drops back to 0 after the pump primes. My gauge is located right after the fuel filter, shouldn't it maintain the fuel pressure?
Pressure drops to 0 after like one second when I put on ACC when priming is done and when I shut the car off it drops to 0 immediately...
E: maybe the check valve could be bad on the pump?

[VTEC_lol]

Update: alright I got the Malpassi FPR and now whenever I prime my fuel pump and switch off the car the fuel pressure stays, so at least that problem is fixed and I don't think it could be my fuel pump to make this problem. I haven't driven the car yet because the FPR leaks from one of the holes so I need to do something about that but I will edit this comment if it fixed my problem or not
Edit: nope, still going lean on 4k rpm, I ordered new dump valve since a lot of people have suspected that, updating then

[VTEC_lol]

Sorry for bumping but I'm getting frustrated because I can't find any solution, any help is appreciated
So far I've done:

Changed O2 sensor
Changed fuel filter
Changed FPR
Changed dump valve (adjustable to fully VTA and recirc, no affect on neither)
Cleaned MAF
Checked ignition wiring
Changed plugs and gapped to .020
Checked coil packs (one is still very oxidized but I don't think that's the cause)
Checked intake
Checked vacuum leaks
Changed fuel lines on engine bay
Re-grounded all gauges
Reset ECU like 20 times by now

I'm gonna check for boost leaks soon but that shouldn't be the problem, shouldn't it make it run rich?

Nissan Datascan tells me code 34 knock sensor circuit, so could it be only the wiring or sensor itself? Before I go changing that, will that have any affect on this problem? (since it's very time consuming to change I won't if it's not necessary)
E: forgot to mention that my intake is a rubber boot and I suspect it could be collapsing, I took off my air filter so it gets more air in so it wouldn't collapse, but no change, still hits a wall at 4k rpm
E2: I also have an old video of this happening
https://www.youtube.com/watch?v=J1AmQ-nnkkA
E3: Could an exhaust leak be the cause? My downpipe seems beat to shit and it rattles loudly around 3,4k rpm...
E4: knock sensor shows no signs of resistance, shouldnt it be around 550k ohm?