ok, ALL plugs/wires have been changed. NEW O2s as well. Fuel filter has been replaced.
before car was breaking up, like it was getting no air/fuel, sometimes wouldn't rev past a certain RPM, sounding 'muffled' (like hand over TB/carb)
Car also had erratic idle, sometimes 2k, sometimes 800.
Anyway, fired it back up last night after everything, idled fine revved fine, no mis, stumble, stutter etc. However the IAC hisses louder than the entire car (even with Hotcam, LTs and Mufflex 4" LOL) put finger in IAC hole in TB (BBK 58mm which has been on there forever) and car purrs like a kitten at 800 (smoothly)
Go to drive car, and it starts to do it immediately, bucking and shuddering, like it's running out of gas. I guess the first thing is check the Fuel Pressure now, correct? (255 Walbro pump)
I have MSD cap/rotor, but don't want to change it, if it's not the problem. I just want to get it running right again, so I can sell it. I will NEVER own another LT1.

 

Forgot to mention, I have 2 A/F guages (one for each side O2) and they were ALL over the board lean to rich, boucing back and forth at light speed.