I just got some flowmasters put on my car (84 firebird). They sound good at idle but around 2500 rpm they start crackling and make some wierd noise. The mufflers are all the way toward the back of the car. Could this cause the noises? There really isn't anywhere else the mufflers will fit. I am also runnin a 383 with a big cam could this affect it? I just want to know how to get rid of this noise. I've tried a couple sets of mufflers.