I swapped out my 3.9 for a 5.9. I finally received the computer and lately the truck will rev really loud (sounds like the intake on a diesel) and is a total dog for power. It does this until I get into overdrive, then smooths right out and will downshift and run like it should. Any ideas on the cause? I have no CELs, and it only happens sometimes with no apparent cause (ie.. hot weather/ cold, raining, restart when hot or starting cold). Just pops up as a dog for a bit then goes away...