My wife "claimes" her 5.3L avalanche with the superchips programmer has way less power then her previous 2006 5.3L 1/2 ton ext cab truck stock. She says she used to be able to pull loaded horse trailer 40km/hr faster up this hill. I cant figure it out. they all feel gutless after driving my diesel!
Is there hp difference between those engines?

My guess more torque management and tuning. I can say I had a 99 5.3L pickup ext cab and it run really good. Tires let loose in 3rd. Got a 2002 Avalanche same engine, trans, gears and was the doggiest thing I ever drove. Found out they started adding torque management to stop all the fixing they had to do on the 4L65E transmission. Traded off in 3 months for a 2500 Avalanche and never had a doggy issue. It had the 8.1L Vortec.

Brian

Its might be a weight difference between truck and aval.,but I think it's different gear ratio that making the difference.You have to spin the little gas engines.

same axle ratios?

My wife's 03 Yukon iron block 5.3 would run circles around her 06 aluminum block 5.3 Tahoe. Otherwise these are apples to apples trucks. The torque management in the 06 is , for lack of a better word, gross.

My wife's 03 Yukon iron block 5.3 would run circles around her 06 aluminum block 5.3 Tahoe. Otherwise these are apples to apples trucks. The torque management in the 06 is , for lack of a better word, gross.
You can fix that with a tune