Also it is worth doing the XCR resin post cure before any final sanding and finishing to harden the resins as much as you can.  

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

How hot is the exhaust getting? 

You may need to post cure both your resin and the lacquer to maximise their heat resistance.  However if the exhaust is conducting a lot of heat, you may still be overheating the resin. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi. I carbon skinned car parts but I seem to keep having some form of reaction with the XCR Clear Epoxy.
My first attempt I built up the layers of epoxy and sanded leaving 400 grit finish before spraying 2K Clear Lacquer. 6 months later there seemed to be some reaction occurring as all the lacquer slowly dissolved somehow leaving the 400 grit finish again.
So 2nd time I decided to only use XCR Clear Epoxy. Again I followed the steps of building up the coat and then sanded to a nice shine.
Now 6 months later the epoxy itself seems to be having a reaction and the epoxy is slowly dissolving and wearing away.
I have included some photos.
Before I start to fix it again can anyone let me know what the issue is. XCR is UV resistent but the epoxy is definitely reacting more during sunny days. It also seems to wear more where there is stronger airflow over the car part.

Any help or guidance would be much appreciated.