So I recently picked up a new project from another tgo member. It's an 87 iroc z and it has a pretty hot motor in it. The car sat for 7-8 years, in a heated garage, but none the less it sat. It lost a distributor and that's what led to it sitting. I got it, put a distributor in it, plugged everything back in as best as I could and have been working on it the last week. I got it running, and idling and driving great under light throttle. But once you get into the throttle hard it has a strange cough from about 2500-3000 until about 5000 then it clears up. But... here's the catch. Every once and a while it will just zing right up and have no stumble and run like a scalded cat. It has a ZZ4 short block, AFR 195's, a 224/230 comp roller, an SLP t ram intake, headers, etc. it had a number of vacuum leaks when I first got it fired and I am reasonably certain they are all cleared up. I thought it was just the bad fuel or sticky injectors, but after running over a full tank of fresh fuel, with cleaning additive, and putting about 50 miles on it, I have to say I think it runs too good at light throttle to be a fuel issue. It has a 255 pump in it too. I did notice a decent amount of pressure building up in the fuel tank. Not sure if that's s huge issue or not.

It had an MSD ignition in it. 6AL box, distributor, and blaster coil, along with an MSD noise filter, and wires. It also has the MSD plug MSD plate tpi harness. The MSD distributor was dead, so I replaced it with a new stock distributor. I tried disconnecting the 6AL box and that didn't help either. The car really likes timing. It seems to run best at 12-14 degrees with the brown wire disconnected. 0-5 degrees it dies when you put it in gear, and 8-10 degrees it runs and idles but doesn't sound as crisp at an idle as it does at 12-14.

The motor was hot when I stopped on it today and I will pull a couple plugs tomorrow morning when I get to my shop and see how they look. Just looking for ideas on what issues it might be?

So the ground on the back of the head is good, to the firewall, the fender ground off the negative cable is good, double checked distributor orientation and its spot on, as well as the firing order. I pulled a plug and it looks totally decent. Dry and colored nicely. It's got NGK FR4's in it. I'm going to check the throttle position voltages and see what that looks like. I'm also going to pull the cap and wires back off and stuff my head back on the back of the T ram and take a closer look at all of the vacuum hoses and what not going on back there. The MAF also has me wondering. The part that is strange to me is how it clears up at high RPM

The chip is an ed Wright tune that worked worth this exact setup before so I'm fairly certain it should be close on the tune