Is it possible to have a single muffler with one inlet and dual outlets then have pipes to go out back to each side like a stock FC would? I know its ghetto but are there any experiences with this method? I was planning on getting a single flowmaster or magnaflow single inlet and dual outlet muffler and have two seperate pipe go back to the stock locations.

 

There's nothing ghetto about that at all. It's called proper planning. It's exactely the way we did my custom exhaust. Why go through all the headaches of welding up a y-pipe, or trying to source one, when all you need to do is order a slightly different pre-silencer.

100% stainless, 100% magnaflow.

 

You could do that, but I think it will be a little loud for a non-turbo engine if you don't use a pre-silencer. I don't think it is ghetto at all, but then again it is not the best configuration for power.

Do NOT use Flowmaster mufflers, as they are not intended for the intense heat and pressure of the rotary engine. They do not make any mufflers for the rotary engine, and their warranty is void if the muffler is used on a car for which it was not designed. See the post by jgrewe here:
https://www.rx7club.com/rotary-car-performance-77/flowmaster-opinions-642523/