Hfc vs test pipes
 

So the ? is what's better to have for the z34 hfc or test pipe I really don't know what to do or what would be the best exhaust. I prefer loud aggressive exhaust.

whatever one you want more is what's best

This is the best exhaust by far:

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TPs will give you significantly more rasp and 2-3 more HP (from what I've seen). Even the resonated ones. It all depends on what you're looking for.

If you want something loud then go for the Test Pipes...They will come out louder than HFC's.

correct if you want loud get a test pipe