A shop, PSI Racing, they do mazdas, but some of his customers
are subies and he showed me a 3" SS mandrel bent w/ hi-flow
cat w/ muffler and for 750 not to bad.
when you crush the pipe obviously you chnage the flow characteristics froma smooth circular passage to a elongated
irreagular passage, often causing some restrictions. the key
term is "some restrictions" but if you were trying to milk every
pony out of your exhaust then I would do a day trip.