Just pruchased an '06 Silverado LT extended cab with 79K miles and looks like I will be getting between 17 and 18 mpg normal driving. This will be my basic transportation unless it is a really nice day and I get the BMW 325Ci 5 speed out for a little fun on curvey country roads of north Alabama. I sold an '04 Dodge 2500 with Cummins turbo diesel to which I had added after-market intake and exahust and a Smarty Jr. tunner. I spent over $1,000 to gain maybe two miles per gallon and don't want to make the same mistake again. I am told by local autoparts store that I should pick up at least five mpg on the Silverado with 4.8L engine if I install similar equipment (K & N air filter, dual exhaust system and tunner). Sure would like to hear some personal experience testimonies about specific bolt-ons that work. Don't want to give up any hp but don't need more either. Primary interest is improving mpg.