Something is broken...your coach is constipated.
Since this is a new issue then we must assume it is not normal...
If the exaust is hot then the heat is not getting out of the system, and this is due to a lack of air flow.
You can pick up a non-contact thermometer for less than $100.00, get one that will read upto 900 degrees or so.
You can use this to measure the parts of the exaust system and look for a COOLER spot, if the muffler is clogged up it is likely in a baffle, so one end will be hot while the other will be cooler, the whole unit should be about the same with the end closer to the engine a little warmer.
Being a 2005 model you may have a particle filter of sorts, like a catalytic converter for gas engines, these get clogged and there are processes to burn off or possible restore them, Google your engine type and exaust back pressure to loook for clues there, this may be a simple and cheap or simple and expensive fix.
Once the issue is found you can either fix it yourself if you have a source for the parts or take a trip to a local truck service facility, avoid the "jack of all trades" truck centers and stay with the factory authorized branches of the engine manufacturer as they will have the data to support your engine by serial number and be able to get the exact parts.
While you are at it you may want to have some additional heat shielding material added between the hot spots and your air lines, their should have been something there already or maybe the heat is way more than designed for, but since the broken parts will be out of the way during their replacement it would be an easy fix to add the shield, the shop doing the service could do this for not a whole lot of additional cost as they may have the material on-hand and have done similar work before, be sure to ask them ahead of time so they can order what is needed or at least discuss the issue and other possible solutions.
The thermometer is good for checking a lot of troubles so handy to have anyway.