I just purchase a 06 Monte carlo and have a problem I can't figure out when I getting some speed starts to missing but I push the gas pedal deeper and goes away, I replace spark plug the cables and one coil I replaced the cat I I put some treatment in the gas rank and no luck but the funny part about it is that only does it on d when I sift it to 3 goes away then my idling its to low have any one gone through this problem before?, thanks for your help