In the past couple of months there's been some thread content regarding aero and cooling mods. Didn't want to hijack, so here's a thread for this subject. The recent "no bumperettes" thread had some questions about getting heat out from around the muffler, so here's pics of my solution.
First off are the rear bumper vents. Unfortunately, between the aluminum bumper and the body there is a body seam that blocks flow. I bent this downwards, opening a gap between the two. I have also removed all of the heat shielding from beneath the trunk and around the aluminum bumper. I've had the car set up like this for more than a year. No noticeable differences in coolant temps, but when the car is in grid, I'll put my hand over the vents and can feel plenty of heat coming out.
The second pic is new for this year. I've opened up the rear wheel housings to increase airflow to the muffler. We'll have to see how it goes.