Who makes a universal muffler that will stand up to the rotary's extreme heat? Does a muffler have to be packed with steel wool to be able to handle the temps?

I was told that Dynomax Ultra Flow mufflers could, but the guy at the exhaust shop just told me they couldn't take the heat.

Anyone know why the mufflers on Dynamax's Turbo Catback system can handle it? Are the Turbo mufflers packed with steel wool instead of the usual fiberglass?

I want to build a custom single exhaust system, but I'm just not sure on which mufflers to use.

 

I've seen dynomax on rx-7s before.

So instead of buying an rx-7 ready exhaust system (downpipe, perf cat, high flow pipes, good exhaust note mufflers) your're trying to save money by making/haveing someone make your an exhaust?