There is a padded heat shield that appears to be glued to the underside of the bed that I assume protects the bed from exhaust heat (and in my case my LineX sprayed liner too!). Mine is falling down onto the exhaust, any suggestions on a type of adhesive for this application?

 

If you can clean it well, 3M super 77 will do the trick. It's available in a spray can. If you can't clean the area, then you might try caulk or RTV.