Backfireing at high rpms.

[MarkRipoll]

I have a problem.. whenever i get on the gas to high rpms then shift i have a backfire. Is this bad for my car, and how can i fix this problem? my car is a 1995 240sx n/a with a header to cat thats aftermarket, but the catback is stock (not me that had that great idea), and a stillen airfilter. (dont flame i didn't put it there either). Also whenever i shift into a high gear then let it slow down alot it makes a popping noise. Is that backfireing too? If so them im backfireing alot.

Thanks

[liquid_cool]

backfireing comes from ither an open valve at the wrong time..or unburned gas hitting a hot manifold....could be 3 things..#1.) bad sparkplug and or gap..#2.) valve falure or broken valve spring...#3.) cam timing or timing advance on your dist.

this is at least a good place to start looking for the issue..start with whats easy..spark plugs..then timing..if all else fails ..its internal and your in for head work..in my opinion...hope this helps.