ok, i have a problem and i need advice.. I installed a custom true dual exhaust on my 03 coupe. A couple of hours after i was driving and the car started to miss fire, i turned the car of then back on again and it was fine again.. know it fine for a while then it starts to stumble(mis fire) again, i keep driving and it fixes its self then it starts again... The cycle keeps happening over and over again.. i still have the factory cats.. theres no cross over point on the exhaust system..spark plugs are new.. im thinking maybe not enough back pressure?
any help would be helpfull...

thanks..

 

You are going to have to make a cross over point some where to correct problem !