When I had my GTI i had a big turbo on it with a big intercooler, I painted it gold because i just love how black and gold look. Well I only painted the front of it since I was also worried about it not cooling so I left the back unpainted. I made 320 to the wheels at 18 PSI. I figured if it starts heating up then my PSI would drop maybe 1-2psi which would lead to less horsepower. But it never did. I lived in El Paso, TX at the time. On the hottest of days I never FELT any loss of power. On cold days I would gain about 2-3psi of boost. Good luck! I dont think you'll notice any difference.
2001 Mustang GT - Airaid CAI, Accel Super Coils, UPR O/R X-pipe, Super 44 Flowmasters, BAMA Tune, Powerstop Rotor/Brakes,SR Short Throw Shifter.