Recently I have been considering upgrading my 2002 Duramax/Allison 4x4 to one of the new 2007's. The new ones are great...but after much review it seems to make sense to keep the 2002 as it only has 85,000 miles on it, is paid for and is in good shape. With that said, I'd like some ideas on what to add of the various components (intake, exhaust, electronics or others) that will enhance performance, effeciancy and most importantly help add longevity. At about 65,000 miles I had to replace the injector pump (under warranty) which has been the only change to the truck other than standard maintenance and new tires. I would appreciate any suggestions on what to add, what not to add and any information on preferred maintenance schedules and fluids as the truck ages. I appreciate your thoughts and ideas.