i have an 02 duramax with the lb7 and allison 5 spd. i frequently change the fuel filter and air filter, and have replaced the fuel pressure solenoid on the variable speed pump. but my truck does not have the power it should. it builds boost but when it gets arouns 2800 rpm it likes to stay there and kinda fall on its face. the truck doesnt take off like it should! i have chrcked the wastegate and its working and it builds about 23 pounds of boost. im completely clueless on this thing and so is the mechanic in my area. the truck has 180000 on it. and has had the injectors replaced. from time to time it blows black smoke and sometimes greyish smoke but not always. any help would be greatly appreciated!!!!!