While I can't speak directly about the test pipes, I have nothing but positive things to say about the HFCs. If the test pipes are similar in quality and performance, I'm sure they'll not only add gains, but plenty of power as well (and perhaps some rasp that often comes with the TPs).
Good luck!
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"Any man who can drive a 370z while kissing a pretty girl is simply not giving the Z the attention it deserves." Albert Einstein....modified.
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