87 GTA 350, B&M shift kit, Linginfelter throtle body, slp runners, msd ignition.

My car just stalled suddenly and would not run without my foot on the gas. The next day i tried to start it and it would not stay running until it got hot. I checked the compression and did a air leak test and they were fine. My I found the pcv hose cracked and replaced it, then found the fuel pressure regulator wasn't holding any vacume so I got an holley ajustable fpr and replaced all the other vacume lines and took out the charcoal canister to get rid of some useless vacume line. I set the fuel pressure at about 36psi it seemed to run best there, I live at an altitude of 4500ft so the air is thin. I started it and it was the same thing. A probe in the exhaust said it was runing lean. when it was hot I test drove it and it hesitated when I steped on the gas but then ran good. If I floored it and right before it shifted into second the tac would drop to 3grand and then go back up real fast, the engine sounded fine though. The only thing I can think of is its a sensor or a injector, but the o2 sensor is two years old and the injectors were flushed a couple years ago as well. There are no codes stored in the computers memory.