Hey guys, first post here, looked around for a while to see if anyone else was having similar problems but couldn't find anything that helped with my problem so here goes.

I have an 88 Firebird Trans-AM GTA (5.7l tpi), a few weeks ago it wasn't running whatsoever due to a bad fuel pump and had been sitting outside for the last 6~7 years. After the new fuel pump it started and ran but very poorly.

I checked for vac/tps/maf issues but all was fine. After trying to plug my scanner in I could not get data/code readouts and the paperclip method was a no go either. I cleaned and reseated a few grounds and I was able to get the computer to intermittently communicate with me, it gave me a code 51 (Memcal error) and still ran poorly. I swapped out the ecm and it ran great, however it started missing for a sec and returned a code 42 (EST Timing error), I cleared the code and it did not return but now it stalls after starting sometimes immediately if I give it throttle, if I reseat the prom chip it runs great, but otherwise it's hit or miss. Anyone have any ideas? I'm pretty stumped at this point.