I just built a brand new motor and now my car is missfiring at idle but not when you rev it up?The motor is a 355 with a voretech si blower on it with less then 20 miles on new motor.I replaced the opti and found that my spark plugs number 8 n 6 werent firing.Cleaned them and stuck the plugs back in and same problem.I need help please!

 

Tripple and 4x check your wire order. I know it sounds simple but even the best of us have swore it was right while looking at them crossed.

6 and 8 have fuel? Compression? Or you have actually seen the plugs out of the block or run an inline tester to see that there is no fire on those two?

 

I pulled the number 6 and 8 plugs out and there was fuel on the plugs so i cleaned them and stuck them back in.The car sounded like it started to sound a little better then the misfire started again.The header on number 6 nd 8 was cold, when all the other plugs had the headers hot

 

Check and see if the plug is actually sparking.
If it is then it is sparking at the wrong time - crossed wire, damaged distributor, something.
Or one of the other components are missing - air, fuel, compression

If it is not sparking start working your way back from the plug.