I've got a stock exhaust with 400 miles................

Yup the stock can gets hot most likley because of the steel can and the outer wrap. Not real condusive for heat transfer.

I messed with my HMF by altering the quite_core. Basically welded a small plate on the inlet to close it, and drilled a pile of small holes around the tube. It's the way many mufflers look inside.
It still flows the gas as it should but knocks down the harsh 'rap" of the exhaust.

 

i have a a ip2 racing muffler an there is a cap in the muffler tip an it sounds just right i just have to get it to stop smoking lol