My car has been actin kinda funky lately, if i were to put the tach at 2k in 3rd gear then give it half to 3/4 throttle it starts to sputter, it will pull then give out then pull, sounds like it's missing off a few pistons. It's got a fairly rough idle now, and also once in a great while my car will crank and crank and crank but not fire, then i let it sit for a while and it fires up. i thought it might be the fuel pump, so i replaced it but it still does it.....HMMMMM, any sugjestions?