First of all, I can’t believe that you have a car that old with over 300,000 miles that still looks that good. My 02 with 218 is put to shame after looking at that picture. It definitely looks like a good car though.
As far as mods go, there are a few exhaust systems that aren’t loud or raspy that still add a little less restriction than the factory exhaust. Also, you could look into short ram or cold air intakes. Personally, I would do a short ram because these engines usually lack torque on the low end, and the short ram can help to recover that just a little bit. If you’re really looking to add power something as simple as replacing the injectors and running some fuel system cleaner can help restore lost power due to 300,000 miles of crap building up in the system. It can also help clear out a lot of carbon in the engine itself. Seafoam is also an option for you, although I will probably receive backlash for even suggesting it. However, I use the spray can through the intake instead of the fuel method. However, you can do your own research and decide for yourself.
Once you’re past those options then there are a lot of options ranging from ECU tunes, larger throttle bodies, etc. I’m newer to modification myself as I generally do repairs, but there are a lot of websites that can give a lot more insight than I can.
I hope this can help to get you started. The best thing I can say is that these engines are bullet proof as long as you don’t do anything stupid with it. Since it’s electronic ignition, you can probably see better results with tuning that I would with my cap and rotor on my accord. Good luck to you!