Best Bolt ons?

So, I've changed my mind for the 40th time about what I want to do to the cinco. I want to see what kind of power I can make off of bolt ons, CAI, Headers, Catback, possibly cams, and mp3 ecu. I've read that my best bet is to get OBX headers and OBX forza Catback. Is that true? My priority is sound, I want to keep the throaty sound and make it more aggressive and not raspy. I remember seeing a few videos of p5's and 323f's that actually sounded like subies and I can't find the videos any more. I want that kind of a sound. So what are your recommendations in that department? I have already started all the handling mods, including rear sway bars from the MSP, K-sport coilovers, strut tower bar, front sway bar, and soon enough wheels and tires. Also from what I have read the 5th gear on this car is located outside of the box, so a 5th gear swap is easy. Does that mean something else? How can a gear be outside of the box? Is there a step by step tutorial required or is it that straight forward?

If you want a growl, just get a cold air intake. Headers and an exhaust will also influence noise, but that depends on the brand, size, etc. I wouldn't on counting a huge difference in power. I didn't feel a difference with a CAI and the MP3 ECU, maybe a tiny bit.

I don't think a gear would be outside of the transmission, you should read more carefully.

5th gear is located on the outside end of the main (or counter) shaft, and is accessible by removing the stamped steel cover on the end of the transmission. Have a look at it, it's very easy to identify. Swapping a 626 5th gear will drop highway RPM a little. I really wish there was a 6 speed box that could be swapped into these cars. It's not a really hard job, you'll need a large metric socket and a roll pin punch. There is a guide out there somewhere.

A 4-2-1 header is probably the best bolt-on you can do.

Would you be able to recommend a CAI? Would you say that you lost any low end torque?

The cheapest one you can get your hands on that isn't made in china. Any power gains or losses would be mostly psychological, but it will sound a lot more powerful

4-2-1 headers benefit low end power, 4-1 give you top end.

With bolt-ons don't expect anything outrageous. It's been proven over the years that they yield very little power for the investment. Many will agree that you'd be better off going FI or even do a KLZE (6cyl) swap. The motor drops right into the bay but there are some things that have to be swapped over. There have been plenty of them built over the years and there are multiple build threads here if you wanted to check it out more.

A good quality header is hard to find these days for the platform. I've read and heard a lot of horror stories about the OBX brand. It seems that initially the quality was there but somewhere along the way it went South.

I have a Megan cat-back system with a 4" outlet on the muffler and a cheap short ram air intake on my 02' 5 speed P5. It's quite loud, very deep toned and causes all sorts of harmonic buzzes and rattles inside the cabin. At any RPM between 2000 and 5000 the drone is so annoying I feel compelled to shut off the engine and coast. As well, big systems tend to push horsepower and torque further up in the rev range, making the car weaker at lower revs. This is most noticeable in 3rd-5th gear.

If you want to spend money on exhaust, try to get the racing beat. Great sound and not loud.
Otherwise don't spend money on engine mods unless you plan to boost.
Spend your money on good tires and suspension.