My 3.4 is having issues with a miss and loss of power. I changed plugs and wires and put a new upstream oxygen sensor on it and it helped alot but it still has a miss at low rpm once ur over 2.5 grand it's fine smooth as silk but u can't just Cruise around or take it slow in the mtns or it misses and feels like something is holding it back. The check engine light is not currently on but some times it will come on for a short period of time and then go off!! Please help it's driving me insane!!!