I've got a 1987 gt that every time i start it up stalls out once, then starts up and runs very rough and pops and backfires untill warm. I had the car put on a tester and no codes showed up other than an egr valve wich was replaced and fixed it temporarily. sometimes it does this and does not perform very well, while other times it does not give me fits and runs great, any one else experience any problems like this, i heard to take off the intake and have them boiled(cleaned) at a radiator shop?