I think i have found a solution.
I found it on this forum: trouble code p0087 - Chevy and GMC Duramax Diesel Forum
Apparently on the truck there is a pressure release valve also know as a PRV.
On the trucks in my time range like 05-07 the PRV gets week over time letting gas back into the gas tank before it is suppose to. When it does that while you are under a heavy load the pressure drops too low giving you the (P0087/limp mode) problem.
Some solutions are 1: A PRV shim kit. costing around $10 where you shim your original PRV somehow making it hold more pressure. Link: PPE PRV Shim Kit 04.5-10 GM Duramax
Or buying a more powerful after market PRV that doesn't weaken over time.
What do you guys think?
I hope this helps other people having this problem.
I guess we will see soon if it helps me