at work we use a product from Lydall to help protect the cab from the turbo. The product is has a pressure sensitive adhesive backing, a 1/2" fiberglass core and a stainless steel outer skin.
This does a great job of protecting metal and fiberglass from the turbos--which are a bit too close.
I wish work didn't throw out my 8' rolled sample..
or i would send you a piece of it just to see how it.
Just throwing some ideas out there. I designed aftertreatment components for Peterbilt the last few years. Fighting heat has been a challenge. I do have some pretty cool materials to try out though.
good luck.