Jeff, didn't you say something about a bad coolant temp sensor causing the 3.1's to run bad? Maybe try there. Otherwise if i were you matt, I'd look into the fuel injectors. Do a balence test on them. You are probably familiar with this, so I'm not gonna go into detail. Replace any that seem out of range of the others. Or maybe just replace them all. Also I'd replace the fuel filter too. That may be part of your problem. Good luck. Welcome to AF!