Well I have been having a problem with my car for a while now. I replaced the cap and rotor, plugs, wires and valve springs. Went to the track and it ran fine, the next day it started to stumble from idle to about 3000 rpms and then it will let go and snap your head back. If you step on it while it is stumbling it will not go anywhere but if you let up then give it gas again it will run fine for a little bit. It doesn't do it all the time but it is gettting annoying. The car also seems to be popping alot more out the tailpipe than normal. The problems I am having is a cylinder 4 missfire, the coolant is reading 40 degrees intermittent, the maf will read intermittent, o2's will read intermittent then some will freeze. It seems to be a power distribution problem because I had to replace the fuse for the maf and different sensors. I also already replaced the coolant sensor and no difference. I have long tubes, hot cam, no cats, ported heads and 02 sims. Any ideas would help because this is getting old. thanks

 

I've got the same exact problems with mine. It went away for about a week and a half, then started up again this morning.

It'll be doing fine for a while, start to stumble. And if you let off the gas for a second and press it again it'll run fine for a few seconds and start again.