I suspect my rough idle is because of an exhaust leak at the header flange (haven't had a chance to put the truck on the lift to see if its damaged of if the bolts are just loose.) I suspect the leak before the O2 sensor is causing it to read a lean condition, so the computer is richening the AFR, choking the motor at idle, and probably causing my recent drop in MPG.
Before you ask, I know I have a leak because I tried running some top engine cleaner through it as a cheap pot-shot at the rough idle, and a fair amount of smoke came out of the collector/flange instead of the exhaust.
2003 Edge Reg Cab 2x4 3.0L 5M 8.8LS - Red
1991 Miata - British Racing Green Special Edition (3716 of 4000)