I have a 1990 eagle talon awd and am currently having problems with the car. I have a 2g maf on it, 550cc injectors, 255 walbro fuel pump, aem wideband, and apexi safc2 on it but the problem that am havingis that the car is running lean that my wideband just goes all the way to lean. The vacuum is 10psi it idles like around 1200 rpm. I currently replace the throttle body with a rebuild one I performed a boost leak test and dint find anything so am just getting frustrated with the car that I just want to get rid of it so if somebody could give me ideas to what to check.
The car runs rich with the maf unplug.......

Usually stuff like this is pretty simple. Don't get too frustrated.

I'm not an expert w/ the 420a turbo setups but with my car there have only been a couple things that would cause it to do this:

First: My wire to my ecu that goes to the pin for my front o2 sensor got cut so my car just leaned out like crazy no matter what until I saw that. (I don't think this is it for you though I just noticed you said that it goes to being rich when you unplug the MAFsensor)

Second: The mass air flow sensor went bad and was tested easily with a volt meter at the pins to see what was going on. Or you could swap in a known good one and see if that fixes your issue.

Try testing/swapping out your MAF sensor and see if that helps. If it's not that maybe it is something to do with your engine management software.

I tried swithching the maf with a good one but it still does the same thing... Am trying to look for more problems but just can't find anything. I also took of my safc and connect everything back the same way but nothing change.....

I've been having similar issue also similar mods. except a MAFT Gen II.

Car runs fine cruising, but soon as you touch the gas, its instantly lean. and stays there for about 10 seconds.

I've swapped turbo, injectors,TPS,ECUs,MAF, problem still remains. I may look at the ECU wiring next as a PP stated. I'm subscribed G/L with fixing your issue, I'm subscribed.

My problem got fix. I found out that my isc motor was bad the motor wasn't working good. So I replaced it and I got it to run better but now I found out that my head was leaking oil to the intake manifold so right now my car is getting a head replace with some arp and cometic head gasket.