What's your budget? H&R's Street Performance coils are a great coil over that are good on track and still good for the street. Lots of Porsche owners tend to go this route for track use, but still compatible/comfortable for street use. Most coils you get will work for either, but ride comfort can be sacrificed with what platform you go with. For example, I currently am running AST's on a track car of mine that are valved and sprung for TT racing so they're really not comfortable on the street. Otherwise, KW is another brand that also makes a few different variants for your 986. V1-V3 (V2's look to be NLA currently) and possibly Clubsports. Personally, V1's are great for street/track use and may be all that you need for what you're wanting to do. The higher variant V3's gives you a ton of adjustability ranges. I actually know people who purchase V3's for different platforms just for a better street ride. I posted both the H&R and KW's below for you and if you click the links there is additional info about each one.
H&R:
1998 Porsche Boxster Base Convertible - Suspension Upgrades & Performance - Page 1
KW:
1998 Porsche Boxster Base Convertible - Suspension Upgrades & Performance - Page 3