I had already cut the flexible duct planning to put the muff on the tail pipe and now it didn't fit so I needed to either buy a new duct which are expensive or splice this one back together. So I bought a 2 inch aluminum piper for a couple bucks and spliced the duct together.
I installed the muff per plans. Installed the flexible duct, one with a splice in it. Fastened the cuts to the intake pipes.
I didn't attach the duct to the engine mount because I want the ducts to vibrate with the engine. There is some play in the duct that runs from the muff to the cabin inlet.
I also installed three heat shields on the exhaust pipes to hold the duct material from touching the exhaust pipe.
I tested this configuration with a vaccuum and it seems to blow air thru just fine.