How much should I do to my Boxster?

[JayG]

Don't mess with Mother Nature
Keep it stock

[78F350]

Coolant tank. Add a new Porsche brand coolant tank to your list.

Unless you want to throw a lot of money at it to make it into something that it's not, just do minor mods such as suspension, lights, aero, and exhaust.

If your IMS bearing is shot, the engine is trash. Then the answer may be different.

Regarding oil in the cylinders: You say the AOS is bad. Is it dumping oil into the intake? Intake leads to intake valves. Valves lead to cylinder.

[morbidelli17]

I have a very nice book on an iconic BMW motorcycle, the R90S, built in the 1970s. The section on maintenance and upgrades strongly recommends against building performance into the bikes. If you do so (I am paraphrasing), the author says, you wind up with an unreliable bike that still won't perform half as well as anything modern. Maintain it, upgrade the bits that are clearly better (ignition, etc.) Then let the old lady age gracefully and enjoy what the engineers had built at the time, the author suggested.

I have a stock 1999 Boxster, and I intend to apply that principle to my car. Maintain, polish and (lightly) restore. Suspension bits will be the extent of my performance enhancements, and that's basically going to be limited to better bushings. Pretty much everything else is going to be stock or stock-equivalent replacements.

Your car is awesome and has a clean provenance, enjoy it no matter what you do!

M