It takes two seconds to stick a cork in one tube. If there is any reason at all to suspect poor fuel delivery performance when using any aftermarket box muffler with two outlets then this should be among the very first things to try, its painless and instantly reversable.

If ya, ain,t got a cork then whittle one from a tree branch. I know we don,t have much of them in these parts but heck betcha I could cut one from the old out house door real quick

John