99 WS6
 

I have an original 99 WS6 18,000 miles and and looks new inside and out. What performance modifications if any can be made without lowering the value of the car.

I think any mods other than swapping on a different set of wheels and tires would hurt the value in the long run.

I have a 2002 WS6 convertible with 29K on the clock and it's still factory stock with no mods. As time goes on you'll see that cars that were left alone with low miles will become sought after and command the highest prices.

Adding a filter/lid will help, and can be swapped back without issue. Same deal with a muffler, but the only real difference will be the sound.

A Strut tower brace can be added, and will improve the feeling of the front end.

Other than that, I agree with B man, keep it stock.

Just keep it stock & have fun driving it the way that it is.

I would keep it stock, so many of these cars were modified. A bone stock on might bring more money in the future.