I've got the 5.3 and it feels pretty strong... but the automatic transmission is the truck's weakest link. If you're not at the perfect speed, it won't downshift and ther truck will just creep along. Other times, it will kick down and just take off. The magic speed seems to be around 35 mph. My Trans Am was the same way... although it didn't seem quite as reluctant to downshift as the truck is. When passing someone, I have to really lay into the pedal to get the truck to wake up and go! I've been reading that the transmissions in these trucks aren't the most durable and reliable... so I take it easy unless I need to get on it to merge or pass. It's a shame, because the LS engines are "Like a Rock" I never dreamed my LS1 would make it past 50,000 miles (especially after my brother got through with it!) but it went 167,000 and is still going strong.