<font color="red"> why would you put a muffler which is going to be the source of 80% of your engine compartment heat inside the engine compartment, especially when people are complaining about elevated operating temperatures already? </font>
I can answer that -- if it's outside, it'll get ripped off. /forums/images/graemlins/tongue.gif We routinely replace or reweld mufflers on our conventional tractors.
There are at least three configurations of muffler on the PT425. The insulated one, and the double-wall one Bubenberg has seem to do pretty well for underhood heat. It appears there is some variation in experience with the insulated one. For those who encounter problems, please post here and let PT know. As this thread shows, they try to make changes to cure known problems.