The vette owers have complained about this heat problem for a while... there's a replacement heat shield that can be used:
http://www.eliteengineeringusa.com/T...emp_Tests.html
I'm not sure if it will fit in an XLR - it may... the XLR chassis is around an inch longer than the C6 chassis - but I can't remember where that extra inch was added.
May be worth contacting them to see if it'll fit in the XLR's - my undertanding is that it costs about $240.