I'm a newbie on here and I've done some research and this sight has came up a lot. I've got a 2008 3500 hd. I've got an air raid cold air kit, magnaflow exhaust (5"-6"), and ts performance's mp8 box (those guys are close to me and their customer service is second to none). A month ago th p0087 code came up and the truck went into limp mode. I'm a snapon dealer so i took the solus pro, cleared the code and rolled on. Everything fine for awhile. Code came back, changed fuel filter, cleared code, took the truck to ts performance they checked to make sure it is shimmed right and it was. They also put the truck under a load on the highway. The code came back but when they took the mp8 box off it wouldn't come back as bad. Yesterday with the box off and out of the truck, pulling the 28ft enclosed, the code came back repeatedly. Today i've given it some abuse with out pulling anything, and the code isn't coming on. When you put some weight on it, the code is coming up. Apparently their is something going on with this truck. What do you guys and gals (can't forget you all!!!) suggest the problem could be. The truck is still under warranty, but my local gm dealership knows about the mp8 box and they really don't like it. thanks for everything anyone can give on the advice side.