hey all. i put a hotshot header on my car a while back, i also have a max speed muffler and 2 1/2 in exhaust, i also went to a local muff. shop and had a hi flo cat put on. a week after that the check engine light came on. i had it checked and the shop said it was the cat. i also noticed a decrease in sound almost by half, and a little power decrease. could my cat be melting or getting plugged up? oh also my muff, has a rattle in side of it. i am so frustrated in this matter, can anyone help.