You did not say what engine you have so I am going to assume that you have a turbocharged engine. If you are looking for a good performance modification go with the 2.5” mandrel bent cat-back exhaust.

You will need to put in a muffler of some kind. With straight pipes you will attract police from neighboring cities! Talk to the muffler shop and tell them if you are looking for a quiet free flowing ride or if you want some noise. Either way it will be louder than stock. Even if you ask for a quiet exhaust it will still flow dramatically better than stock, noticeable improvement.

I assume the regulator you mentioned is a rising rate fuel pressure regulator. That should be way down on your upgrade list. Definitely after the K&N air filter, synthetic oil and ATF, 2.5” cat-back exhaust, better brakes, full suspension upgrade, rims & tires, boost gauge and air/fuel monitor, upgraded ECU, bored throttle body, 3” down pipe and race cat, etc………..
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Nathan Valles, Black 855R, Tint