I own a 2007 suburban that has no acceleration when merging into traffic or when passing. potential rear collision on interstate highways. engine tapping is moderate to severe, sounds like metal to metal impact. have filed a complaint to gm, and was told they are aware of the problems. they offered to pay one month's truck payment as compensation for the problems. just before parking when vehicle is in slow roll it will suddenly lunge forward. vehicle is definitely a lemon.*ak