I did the same thing as matty mo did, but wondered the same thing you did. The different diameters and resulting air gap do not seem to hurt anything in the way of disrupting a smooth and seamless exhaust entry, and actually sound pretty good. Of course a dyno would be the only way to prove this out, which I did not do. When you google these things, hundreds of them come up, and if you are diligent, could probably find one that fits snugly inside the end of the exhaust header itself. Can't tell you off hand what the inside diameter of the header pipe is, but a good set of calipers would tell you that. Good luck!Thanks for the answer!
There are two questions .
Why I put it on in the muffler inlet ?
The discrepancy between the diameters and the presence of free space between the tubes does not affect the work?
That is where I had room. I could not pull the perforated core pipe out of my mufflers.Why I put it on in the muffler inlet ?
Maybe you can find a baffle that will slide into you mufflers removable baffle? They are available in several diameters.The discrepancy between the diameters and the presence of free space between the tubes does not affect the work?