[Sandy G]

I have a 2000 S with 40,000 miles. If the smoke is bluish, it's probably oil. Consider replacing the spark plug tubes. The seals go bad over time and when they leak, you'll see a lot of oil smoke on startup. They're cheap and not hard to replace. My Boxster smoked after I first bought it, but it was just the tubes. I replaced them and it hasn't smoked since.

White smoke is likely a coolant leak. Since you just worked on the cooling system, it's possible something isn't tight and is now leaking. If so, you may be able to spot crusty dried coolant near a leak.

Good luck!