After my header install the car ran like a bat out of hell. But I have noticed now that sometimes in 3rd and 4th gear that I am getting a misfire, haven't been able to catch what rpm it's at. 1st and 2nd gear pull very well, but sometimes (and sometimes) when I get into 3rd, about one second after being in 3rd it misfires. Then sometimes it won't misfire in 3rd but then misfire in 4th, not sure what's going on.

I changed my spark plugs and wires during the header install, any ideas?

 

you probably burnt a wire. sometimes you can't tell just by peeking at them because the underside may be burnt. look at them all very closely.

 

Also check for a wire that came off a plug....after my install i noticed the same thing and thought it was a burnt wire...after checking, one of the boots came off the wire a little bit and once i put it back on everything was fine.....

if its the wires, invest in the Taylot OVC wire kit...its saves alot of headache later

 

I do have the OVC kit.....but I just figured out that sometimes I'm getting as much as 9 degrees of spark retard........I think my timing is a little to advanced...