For NA you are probably better with HF cats but for tt the test pipes are better as the give a free flow and are better for the turbos.
As mentioned the test pipes are cheaper because they are just a straight pipe but the resonated test pipes are almost as expensive as the HF cats. If staying NA I suggest using resonated test pipes if you go the test pipe route becuase the regular tp give a very rapy nasty sound to the exhaust.
As for the smell when I first installed mine there was a very strong fuel smell as there was no cat to catch unburned fuel but that went away after a couple of weeks as the ECU got used to the it I guess.
If the car is an 04.5+ you will probably get the CEL go off due to tp's.
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