Hello. There is no doubt about how great the 3.8 is. Had several of them go to 300,000 miles. As for the GXP and the 5.3 LS4 it seems to be a great motor. The Water Pump is expensive when it goes out. It is different the the normal LSX motor's water pump to make it fit into the W-body plat form. And also the Serp belt looks to be a pain and there is some special tool for it. I havent read about any blown motors yet. There was some issue with guys using N2O bout a month ago with number 7 plugs. Biggest issue is finding performance parts designed for the motor. The trans is the weak spot in my mind. It seems hit or miss. Some people are nice and they have failed before 30K others run them hard and replace them around 100K. However the trans is updated with some better hard parts and with a little aftermarket /GMPP they should be pretty good.
