The Northstar is a pretty well, and tightly put together enigine package, put in front of a great tranny (4T80E). The valve cover gasket problem is an isolated issue. Not a general problem. At 36k miles I have had 0 issues with the engine and nitrous a bit. The trunk leak issue is the rubber gasket seating, making sure it stays tight around the top seems to keep mine dry. It did come off the track towards the top once and I did have water in the spare tire well.
Check for water in the trunk, or someone not drying it out good, lower panels on the fender and doors coming loose, pull the back seat and check for corrosion around the ground to the body, there have been a few bottom oil leak incidents (oil coolant lines), and a few rear exhaust loose complaints. Also check to see if the moonroof wind deflector is intact and working. If you find one exceding 75k miles or so, having the dealer replace the spark plugs would be a plus. All in all, After some fitment issues were fixed, I am very happy with the way my GXP is holding up.
Last edited by GXP Venom; 07-28-2008 at 10:15 PM.