How good is the 91 muffler?

[billschroeder5842]

So, my (continuing) search for a reasonable exhaust mod continues and I'm narrowing it down to a few considerations.

I'm probably going to swap out the the 91 restrictive resonator for a 95 spec (2 1/2 inside diameter) resonator. This is a given as the original has a 1 5/8 interior diameter and chokes the flow pretty bad.

I'm thinking of keeping my stock mufflers because I really like the way they look. Plus, I'm a bit of a purist at heart.

However...

Are the 91 mufflers "reasonable" in performance and back pressure or am I being deceived my the good looks? I realize there are other mufflers that are "better" in performance, but I don't want to change them out for hundred of dollars or for a minimal 5 hp difference?

So... are the 91 Muffs a "go, no or I don't know?"