Any cats will be restrictive compared to test pipes. I went from stock downpipes and cats to Megan racing downpipes and test pipes on my convertible TT. Even at 7 psi the difference was noticeable. My area started doing emissions testing again, so I put the stock cats back on, I could tell a little difference in power, but I liked not smelling exhaust when driving with the top down. IMO the pre-cats are the worst offenders for restriction, literally two 90 degree bends through a small cross section and a cat.
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