Ok... i was letting my friend drive my car and he redlined third gear and then shifted into second... hmm smart guy huh? well anyways now my car sputters and backfires when i rev it up... my brother said i might have sucked a valve??? HELP!!!

you have an se-r correct?

When rolling rocker sr20's are overrevved they will pop rockers off and it makes the car act like that. Unfortunately since yours isn't a rolling rocker engine, I'm not sure. This link can explain it better than I can:

http://www.b15sentra.net/forums/showthread.php?s=&threadid=66071&perpage=&pagenumber=1

OK... I found out what it was a rocker popped off... i put it back on but i cant find one of the shims so when i started the engine it was tapping... thanx for the link though man the info from the forum helped out alot... oh yea and i do have roller rockers... motors been completely rebuilt... top to bottom... turbo.. IC... etc... untuned 12 second car... still got more work to do