I decided to go ahead and get a SCT flash programming tuner for the PCM. Looking at it on the dyno, the technician was able to see what was happening between 3-4000 rpms and made tweaks to limit the low value for spark timing in the mid rpms and adjustments in air/fuel mixture. Now the truck runs great and accelerates through the whole powerband effectively. It's like I have a new truck. Nice.... I'll run a few tanks of gas through to see where gas mileage ended up. I was getting 13.7 mpg before the tune.