I am wondering if a bad injector (Holley 50# er's) can be intermitant. My car runs great for about 8-10 miles then starts missing real bad when you start to press the gas. I've been trying to find this problem for a while and have replaced the Opti, O2's, Coil, Ignition Module,etc. I have checked the grounds.The plugs and wires are fairly new and since the car runs great some of the time I don't think its plugs or wires. I have good fuel pressure and vacuum. I get no codes with Tunercat. This is beginning to drive me nuts

 

I have a hunch it is your plug wires.Check all of them with an ohm meter.

 

joeSS97 I've got a new set of wires sitting here so I might as well give that a try.

 

Update, I looked at my plug wires and #5 was fried at the boot. Figures it was the one thing I didn't check because it only did it after warmed up, Thanks joeSS97 , Good hunch