New Protege5 owner, trying to figure out options for rebuild/exhaust

2003 protege 5
So I just recently acquired a manual 2003 protege 5 (it’s my profile pic) and it’s currently sitting at 250k. It runs well enough for me to get from A to B but has a check engine light and is leaking or burning oil.
My intentions are to keep it and build it just enough to have some fun cruising and make it look super nice. Main reason for this thread is to get some ideas on what I should do for the rebuild/swap and get some good ideas for aftermarket exhaust and suspension (since it’s shot), and figure out what could be fixes for the CEL codes. So my questions are as follows

1: rebuild/swap
I wanna make close to 200whp with this car, is it possible na and if so what are my options for that and how much does would a rebuild that will put me towards that goal cost

2: CEL codes
P0421 says “warm up catalyst efficiency below threshold (bank 1)”
P0660 says “Intake manifold tuning valve control circuit/open (bank 1)”
Any ideas what the issues are on these and how to solve them

3: wanting a nice aftermarket exhaust
What’s it gonna run me
What are some good options to get a better sound (not bees in a coffee can or fart cans)

4: suspension
I want this thing lowwwww, so what is a good adjustable set up that’s gonna ride well (it is still my daily) and what’s it gonna run me

Thanks in advance and I’m sorry if this is a long one 🙃
Gidday! Welcome to the P5 life, they're great little cars.

You probably won't get 200 horse NA out of the FS-DE, it's not a great engine for making more power :p Unless you get reaaally lucky and find a set of cams second hand. Here's a really comprehensive race engine build for inspiration iracemine's purpose built N/A ST2 thread | Mazdas247

You could swap a JDM spec FS-ZE and get 160-170ish easily enough. Another option is a turbo kit or mazdaspeed Protege swap, which will get you about the same power levels. Another, other option is the KL series V6 which will fit with a bit of work. Check out @31N007 's KL Swappin' Protege5 | Mazdas247 build thread for details

Racing Beat, Magnaflow and Megan Racing make cat back exhausts, I made my own so can't comment on their quality or sound :D

Suspension mods is where these cars really shine, stick a rear sway bar and some decent shocks on it and it'll outhandle a lot of 'sports' cars. There's a couple of coilover manufacturer running from cheap, OK stuff to the fancy full adjustable setup. BC gold, Yellowspeed and Ksport to name a few.

Have a read through all the build threads, there's so many different ways to build these little cars!
Thanks for the info, kinda wanna stay away from turbo, but 170 is probably decent enough for me in all reality, I don’t plan on racing it, just want it fun to drive (it is my daily) I do really like the car and it already handles pretty well, iv got about 5k rn I can throw into it, but first thing first is getting the engine sound, and fixing the exhaust and suspension that the previous owner slacked on and that wretched CEL
170hp without turbo in a Protegé is probably not going to happen. FYI, the Speed Challenge Protegé had ~225hp, but it peaked at something like 8000rpm and needed to be rebuilt after almost every race. Asking that much out of a street engine is just not feasible.

If I was in your position, and the body and foundation are relatively rust free, I would rebuild the engine with forged internals with mild street cam, then tweak the suspension the best you can afford. Where this chassis really shines is with the handling. Also, rebuild the gearbox with an LSD.
Ok, well what kind of hp can this thing reliably make? The car is pretty clean and I got a smoking deal on it. I love the little thing,
With bolt-ons, maybe 120-130hp at the wheels? Add in some cams, and maybe 140-150hp at the wheels. These cars were not given a powerful engine. I would build for reliability and smoothness. A good set of pistons, stronger rods, make sure the head has been cleaned up, valve seals replaced, add a light weight flywheel and modest clutch, LSD, and full-on suspension.

Plan on spending well more than the car is worth to accomplish all that, too.
Yeah, having had three Protege5s now, rust is the biggest enemy. My first one was an MI native, and it showed. The second came up to MI from NC and spent three winters being daily-driven and even that was enough for the underbody to give me a bit of a frustrating go at times. The current one I have lacks clearcoat on horizontal surfaces, but seems pretty unscathed as far as rust is concerned.

I have had more fun throwing my car around corners (both on the streets as well as Autocross) than I think I would have in a straight line.

My biggest "plus" from the KL swap would be the torque, compared stock-for-stock against the FS engine that comes normally.

If I hadn't had the suspension I probably wouldn't have KL swapped it. Handling > "absolute" speed, IMO.

P0421 is signaling that your primary cat is toast. If it's an OEM header then that's possibly the case. I actually hollowed mine out on my second Pro5 and kept the secondary cat in place. If it's got an aftermarket header, you can run a spark plug nonfouler on the downstream O2 sensor and that might eliminate that code.

P0660 is either VTCS or VICS solenoid-related. There's a white and green solenoid on the top of your intake manifold. You can swap the solenoids, being careful not to break the plastic clip built into the solenoid as well as the nipples for the vac lines. If the code changes to another one (can't recall the number) then it's a solenoid issue. If it remains, then it could be that the diaphragm has failed that actuates the runner. Cross that bridge if swapping the solenoids around doesn't move that code over.

Racing Beat made an aftermarket cat-back exhaust for this car that supposedly sounded nice. Admittedly, I'm running just aftermarket headers to a stock exhaust from the resonator back and am pretty happy with it, but that's with a V6 under the hood...
For suspension I'm running the Eibach Springs Pro kit and it's been pretty nice to me. A bit jouncy over some highway sections, but otherwise tolerable for daily-duty. If you can source an AWR rear swaybar, that'll be the ace in the hole if you're after a properly nimble Pro5.

I hope you enjoy the car for time to come and that it's not too much of a burden on ya! I have to say, despite enjoying my MK7 GTI, there's something that still makes me enjoy driving my Pro5!