ok i changed my exhaust yesterday finally. I went from a 3" exhaust with flowmasters that dumped out just undernieth the front seats to a 2 1/2" exhaust with magnaflow's that exits out the back of the blazer. Yes it is still dual exhaust. No cross over pipe. However it is running wierd. Almost like the timing is off. When you change your exhaust like i did how much do you add or subtract in your timing? To get it to run better? I never had this problem before and now after the new exaust the idle is real weak and wants to kinda stall out.