Yup, never expect it to have a snag free status.
Do the miles and the niggles melt mostly.
As a matter of interest why do you feel the performance needs improving. The S2-S3 engine comes alive at about 3600 when VANOS kicks in so just stay
Mind the SUMP, do look into a sump guard if you have road problems in your area. The engine is far back from the front axle and so as you drop of a speed "pillow" you can land the sump. Ditto the crown of a hill. You have the singe VANOS 4.4 engine and the oil pickup from the front of the sump drives the mechanism so no oil due to a dent or damage will possibly wreck the VANOS. Sumps are not cheap (£500+ swapped)
The clamps that hold the lid to the screen are easily replaced and quite cheap. They do improve the sealing. If the clamp just flops about then the springs have gone and it is best replacing them.
Water can get in around the leading edge of the doors and ruin the flat leather along the sill between the door and seat. It starts to wrp once dry.
If you want to retain the paint then consider paint protection film on the nose, leading lower edge of the rear arches, and possibly the sills to avoid hoof marks.
The audio does benefit from an upgrade. The sidepipes get noisy about 3000 on that engine so you can still listen to it at least part of the time. It will pull from 1400 in almost any gear when you are feeling relaxed.
Enjoy.
