Cascadia DD15 acts derated when MT.

I have a 2014 freightliner cascadia DD15 10speed. The truck acts derated with no check engine lights or codes when I'm empty or light loaded (under 15000 in box). Low on power and boost psi only gets up to 15-18 psi (usually 25-28 psi when light and 30-32 psi when heavy) in top gear with pedal to floor. This doesn't happen every time when Im MT or light, mainly when I've been driving for a couple hours then shut truck off and start again. I have not had this problem happen when I had a heavy load but am worried I might. New to the forums so would appreciate any help or knowledge. Thanks!

 

Have you had this happen before?