Well put the coils in but didn't get a chance to drive it for a long time, but one thing I did notice was part thottle acceleration and response has changed. The truck has a round 64k miles and it felt like it would strugle from take off. I'll put some miles in this week and see if I get some mpg back.

 

Any internal mods to the engine? Something we have had customers complain at work is this symptom for factory engines. We tried everything, and on two of them we found the lobes on the camshaft starting to scallop. With no events of missfires in the PCM. On some of the other ones we have had the customers complained of a ticking noise at idle. On these we found the lobes scalloped real bad.

 

Well, the truck did the SAME exact thing with the 4.8 (144k) as it does with the LQ9 that was put in it's place (75k). Everything off the 4.8 was re-used on the LQ9. We basically stripped the LQ9 down to a longblock because I didn't know the history of the engine, only that it was good running. So I wanted to reuse all my accessories, intake, wiring, etc that I knew was good. So in summary, it's nothing internal. It's either the coils, wires, plugs, or something in the tune.

 

Since there are no other obvious symptoms (misfire, loss of power, etc.), my guess would be in the tuning...

 

Well guys, sorry to bring this thread back up, but you were right, it was the tuning. I took out the old Wheatley tune and put in a new Wheatley PCM yesterday and the truck is much smoother on the highway. No more slight hesitation or whatever it was.