Sorry, things are all over the place on the site these days but this seems like as good a place as any.
How to you go from a 3" exhaust pipe to a 2 1/4 inch exhaust pipe....not simply it seems. After playing with all the adapters at the local parts stores and coming up dry I just bought a 3" connector tube and decided to see what we could make.
So we focused the mathematical powers of Jim squared and figured the circumference of the 3" was approximately 12.5 inches and the circumference of the 2 1/4 was about 7 inches so we divided the difference by 4 then ignored all that and marked out some approximate pie cuts in the adapter.
Then we cut them out and bent everything inward.
An end cut of the 2 1/4 and a little welding and it was all done.
Now why did we do this? Because we got a stainless steel Banks muffler for $20 and it had a 3" inlet.