I recently bought a 28ft rockwood 5th wheel 6700lbs so I had the sell my beloved tacoma. I figured a diesel would be perfect to tow the 5th wheel 3-8hr drives, after looking around a bit I found out my sisters husbands father would sell me his well maintained 2008 GMC 2500HD with 113k miles on it, he no longer needed it since he works in the city and only bought the truck to tow his 5th wheel which he no longer has. Hes been driving a civic for the last 2 years and the truck sat on the side yard only being started and driven to keep form getting stale. Before selling it to me he took it to the shop the guy recommended all fluid change plus fuel filter and housing. So I went to Reno from Redding to pick it up , drove it back from Reno, no issues. Once I got it home, I drove it back and forth from work for about a week. Even took the 4,000lbs boat to the lake over the weekend, no issues. Until I hooked the 5th wheel up, and tried going to the coast. As soon as I hit the mountains, boom! P0087! Limp mode on tight, steep, narrow and windy roads. Not fun. Did a little bit of research on the forum, went ahead and replaced the fuel filter (even though it was still new), will be adding the PPE fuel rail plug, and FASS lift pump. I've checked the lines and none seem to be pinched or soft. The previous owner has never had this issue and I believe him. I'm really thinking that it might of been something that they did at the shop when he took it in. Any help would be appreciated.