I have a 1994 V6 Camaro and it has been acting funny. While I'm driving it every once in a while it will feel like its shaking in the back, kind of like it isn't getting gas or something, if i let off the gas or give it gas it stops but if i give it gas it sounds like its hitting something or backfiring infront of the drivers sit somewhere. It usually does this when I'm speeding up fast or going up a hill. Anybody have any clue what it could be?