Running lean with intermittent misfire

[RipMr2]

1990 300zx Twin Turbo
Engine is from a '96 Z32
Single K&N intake
Stillen Exhaust turbo back
ASH-SPEC ECU (Reflashed recently)
JECS 750cc new style injectors
Auto Meter A/F gauge (Narrowband)
HKS Turbo Timer
A'pexi SAFC
Greddy Profec B Spec II Boost Controller

I bought the car a year ago as a stage III.

The car was stored for the winter and was not worked on until late winter. So I upgraded from stock injectors (which were new style to begin with) to JECS 750cc new style injectors. I had no issues putting the injectors in. Had the ECU reflashed by ASH for the 750cc injectors. This was my first plenum pull and put everything back together. I painted my valve covers red and used new intake valve cover gaskets. I used a new plenum gasket, a new AAC (IACV) gasket and new fuel line insulators. When I started it up the first time, it was a little rough with a bit hesitation and a misfire every 2-5 seconds. It was running very very lean according to my A/F gauge (narrowband). There was and is no fuel smell. The oil smells like oil. So I checked for boost/vacuum leaks. Threw the compression up to 5psi and found a huge leak right after the MAF (Nice job). Fixed a few other leaks with a few clamps and the big leaks are gone. The center of the plenum is silent which is good I think. The IACV was leaking a little but a clamp fixed that. Now the dipstick leaks which I think is normal and there is also two more leaks near the passenger side intercooler or recirculation valve. I could not pin point the leaks but I left them as is because they were more on the quiet side. I also lost a healthy amount of psi when not adding any air to the motor. I've also adjusted my TPS to .45V and 4.5V at WOT. I adjusted my timing which was also off to 15 degrees. I've cleaned my MAF but have not tested to see if it is at the correct voltage (possible?). Checked codes and got code 55. So I did all of that and the car started up faster this time. At first, it was running like it should, about 1000rpm because it was cold and was not running lean. It was running stoich but I think it was because the car was at a higher rpm. After it began to warm up, the rpms dropped like they should but so did the A/F ratio. When the rpms hit 650, the gauge was not reading because it was so lean, I guess. Now it has an intermittent slight misfire. Something I would not be able to find. After revving it up a few times, it began to run like normal. Running stoich and running smooth. Then gave it another few revs and it began to run lean and had that slight misfire. Now when I rev it up, it sounds great. When I hold it at 2000 or 3000rpm, there is a misfire I can barely hear. It is just barely noticeable when behind the car and in front of it. Still idles a little different but I think it because of the larger injectors. When I drive it, the A/F ratio jumps between lean and stoich. I have not gone into boost as I'm afraid to. I'm not sure if it is safe to drive? Because tomorrow I need to get a few parts for my DD because my DD is not driveable at the moment. I'm just afraid of the idle lean condition. And I'm not sure if I do go into a little boost if it will lean out on me and detonate. I do have a SAFC installed but set at default settings. I don't know if that could affect it at all. I'm beginning to run into walls here. So I need help. Which direction should I go from here? Also, I replaced all spark plugs, boots, coil connectors and injector connectors last summer.

I'm not sure if I'm missing something. I feel like I do but..

What do you guys think?

Sorry about the book I just wrote.

[maverick443]

RipMr2, I know this post is old, but I have essentially the same scenario with the same issues. Only difference is that I used Nismo 740cc injectors. Did you ever find the issue? I am nearly out of options, as I have checked just about everything!