Shigun

So I'm pulling my hair out trying to figure out this issue. First off, the engine:

S14a SR20DET
2871r
555cc Injectors
Walbro 255
Z32 MAF
Vented to atmosphere BOV, does not seem to be leaking
RS Enthalpy ECU
NKG BKR6E spark plugs gapped at 0.28", I'm installing some new ones to 0.30"
Boost level is ~10-12PSI on wastegate
Let me know if any more information is needed

When I first got the motor and got it up and going, I had a nice 20 in/Hg vacuum, car ran and idled good, no problem.

Over a span of time the vacuum at some point dropped to about 15 in/Hg, and I've developed an issue where on start, hot or cold, the car will have a very poor, sputtering idle. In addition, I can hear the exhaust popping every now and then when sitting and idling.

The car itself acts like it wants to die, but if I tap the throttle, it will bump up and idle fine until I let off the throttle. Wideband is reporting anywhere from 17-20 at idle, 14-15 cruising, 11-12 at WOT.

Checked timing in timing mode and it's right on 15, but as soon as I plug in the TPS again it goes up in the 20-30 range. When driving around, it usually stays in that range, sometimes dropping down to the 17 range, very very rarely in the lower area of the teens. It almost never actively gets anywhere near 15, even when idling.

I built a boost leak tester and found a few issues here and there that I fixed, but none of them really seemed to have any effect at all on this.

When the car starts stumbling and wanting to die at idle, the vacuum will start dropping rapidly down to the 10in/Hg and below area.

Any time when I am actively driving it, I can't tell that there is any issue just from how it responds and acts.

I've uploaded a data log from a normal driving session I did, though there is one point where I got stuck behind somebody going stupidly slow, so you'll probably notice that. It's pretty large, about a 20 minute log with 69505 lines, so it takes a short bit to load.

https://docs.google.com/spreadsheets...it?usp=sharing

I'm not 100% certain on the general voltage range and responsive properties of the O2 sensor, but it looked like it was a little odd in that it would go to 0 at times. I also noted at idle that I can unplug the O2 and there is 0 change at all, but the consult reported a constant, if I remember correctly, approximately 0.31V.

Any input at all would be incredibly appreciated, and if there are any questions, let me know and I'll answer anything I can.