Hello! Newbie here

Yes, I really think having a big community like this is very helpful. There are a lot of resources in many threads on here already.

When I first got it I really had an issue with responsiveness and generally it didn't feel like it had much power (I don't know how to describe it)

So I cleaned the MAF which was probably long overdue, it was covered in a thick gray layer of something...
At the same time I took the opportunity to change the air filter, the old ones gasket was cracking and falling apart.

After this it already ran much, much better.

Then I wanted to check the sparkplugs, they looked fine. I changed them anyway because they're so cheap, I put the same type in as I took out (Nickel I think?), though now I'm feeling like I should have just gotten the iridium ones. I also checked if there's any leakage or whatever on anything, but I didn't see anything.

Now recently I changed out all the o2 sensors because I wanted to have a look at the precats. The ones on the exhaust manifold came out very easily but the third one was quite the struggle. The two sensors in the manifold had a weird thick white layer of something on them...
The precats look worrying... There's no big damage to them, but In one spot they're not like a flat grid but more like a pointy grid where the cells join eachother, o I'm thinking I should probably get a different exhaust manifold. I've been considering Malian and Zero Exhausts.

The main issues that are bothering me right now is that when the engine is warmed up and I come to a red light, sometimes the engine will feel like it's dying when I'm trying to accelerate from a standstill after idling for a bit, no mater how much I press the accelerator pedal down, I don't get any more RPMS until about two or three seconds later. It's very embarrassing when it happens...

The other issue is the Remus exhaust that was already installed when I got it. It's loud. I can't drive with the top down if I don't wear earplugs because it's deafening in some rpm ranges, measured with my phone it was consistently about 75-80dB at the driver's seat which is damaging for the hearing over time...

Also the roof lining on the hardtop is hanging down but presumably that's an easy fix with the right adhesive

For the moment I think I'll try a quality drop-in replacement for the header, I'm not sure how I feel about the gutting thing yet... I might do it to a used header with bad precats that I could buy separately because ideally I'd like to keep the current one just in case I absolutely need the precats because of local laws or something. I haven't looked too deeply into the approval process for such a modification yet, I'm assuming it involves emissions testing... But yes, they do need to come out as soon as possible.

Thank you for the tip about the exhaust inserts! I didn't know there was such an easy fix, I'll definitely have to try those, I feel a bit obnoxious with my current exhaust note...

And yes, I have a few mechanic friends that will be happy to help with something if it gets too difficult for me, especially since I don't have a proper space to work on the car.

The thing that is weird to me at the moment is just the thing I mentioned about how it seems to almost die when I try to accelerate after idling for a bit at a stoplight or similar. I get no current engine codes or anything, only code I saw once was a P0175, but it was listed as a historical code and It never actually came back.