IsaacMTSU

I have recently got an S14 with Redtop SR20DET back in running condition (after a shop wired up the coil signal wires wrong and couldn't figure it out). It has been sitting with no oil and the top cover and all hoses and wiring in the trunk for over 3 years. I have it running now... Anyway, I have no clue about what this car has on it. From what I can see, it has:

Stock ECU (E5)
Z32 MAFS
Full turbo back exhaust (with aftermarket O2 wired to ecu that may be a wideband?)
GT28RS (GT2860R is the same thing right?)
Stock injectors (I'm pretty sure)
Walbro pump
Lots of empty female connectors on ECU wiring (maybe a piggyback was there?)
GReddy Profec B-Spec II boost controller (boosts to 12psi)
It has some kind of aftermarket cams and adjustable cam sprockets
Other crap that doesn't matter for now...

The car has been driven a lot set up the way it is now. I have a narrow band A/F gauge wired up to it and it stays still just lean of the middle at idle and leans out slightly more when I got WOT and get up to 12psi (it never shows "rich" at all). I read that a narrow band gauge will just bounce around all the time though and this one doesn't. I also read the Z32 MAFS will run lean when used with a stock ECU. Do you think the ECU had a piggyback that is now missing? I know 12psi is too much for the stock injectors, but maybe that is just part of the problem. I upped the fuel pressure using the FPR screw and it leans out less at full boost than it did, but is there something missing in the whole setup?