Jason MK

Swapped a 2000 5.3 into my 72 nova. Swap went great, fired on first try. Harness is from PSI conversion.

took her for a test drive on open headers with o2's in it, had to turn up idle quite a bit. Ran great until under about 40 or 50% throttle. It surges about every .5 seconds, with a big lack of power.

It seems like it is lack of fuel, but i hooked up a gauge and drove around (getting it to surge) and it stayed around 60. (i have a corvette fpr and walbro 255lph)

I figured it was the o2's seeing air so I disconnected...nothing different. Got a full 2.5 inch exhaust with x and mufflers...no change.

tried to unhook MAF, assuming it could be problem, no change.

the only thing i don't have hooked up is the VSS, but people claim to run without it with no problems.

The only thing fishy is how the idle screw is still pretty far out vs. how it was stock. Vacuum leak comes to mind but i would think it would idle too fast?

I'm out of ideas.

Thank you for any help/suggestions/ideas.