Yeah, they gave the truck an even more kick on take offs, wife hated that, I have a heavy foot. Though the Hemi is pretty impressive IMO. I've had a few Dodges and there is always room for improvement. Though I would like to see if those JTR longtubes would fit on the Hummer due to its close comparison to the Colorado.I bet you would get some decent torque out of thatI5. The only thing though is the underside setup.I found pics with it on a 2wd Colorado but not a 4wd.

As far as theas casted manifolds they arerestrictive and with the designs going or moving towards putting Cats closer in order to heat them up faster it doesn't matter how good you make them. It still comes down to COST.