Where is it hot?
Where are you finding it hot (To melt the boots)? Is it the tuned pipe off the block or is it the muffler itself you are finding too hot? The main tuned pipe is cooled by an internal exhanger (Channels inside the port housing) which is fed by the blocks cooling outlet, then the back portion of the tuned pipe assemblies is fed off the main tuned port by a smaller 1/4 inch rubber hose. One of these hoses may be restricted. Is there a Rave valve on your muffler?