On my 1981 Euro 930, with a B&B Tri- Flo dual exhaust, I've noticed recently (purely by accident when I leaned down to look under the rear of the car and put my hand on the bumper) that the rear bumper on the driver's side gets really hot to the touch on the top and bottom of the bumper. It may have been doing this for a while, I don't know. It gets really hot, even when the temp gauge doesn't go above 180 degrees and my intercooler exit air isn't above 70 degrees or so. Just a 30 minute commute on a 60 degree day, with no signs of engine or intercooler heat issues will make the rear bumper this hot. (Not stove top hot, but pretty darn hot).

Any idea what's going on? Should I just try to put some heat barrier material in the back of the engine bay (or between the bumper and the exhaust pipe) on that side of the bumper, or is there some other issue I should be concerned about? The hottest part is on the far left side of the rear bumper (driver side) and it gradually gets cooler going toward the other side. At about the mid-point of the bumper, it's still fairly warm, and on the far passenger side, it's cool as can be.

On a most likely related note, I've noticed that the driver's side exhaust gas is always much hotter to the feel than the passenger side exhaust gas. Any ideas why that is?

 

Well I am going to take a shot in the dark here - your turbo is located right where you are feeling the heat.

 

Bill is correct, the turbo is on the right hand side of the car thus generating much more heat.