Having a heck of a time with this thing. I bought this SUV about 2 weeks ago and it has a upper knock but thats not the problem the problem is it runs like crap when idleing when i rech about 50 miles an hour then it seems to run fine. changed all the plugs and coil packs also change #8 and #6 injectors. I took the valve covers off and I had a rocker arm laying to the side. replaced lifter and it quieted the noise down but still runs crappy. I removed the electrical connector to the #6 coil pack and there was no difference in the way it ran. what would cause that? and it is only the #6 the other ones when disconnected bog the motor down like it should. Also no check engine light is on and no code.