Here we go... a real puzzle. 2001 9-3 2.0L @ 171000 miles. Occasional heavy exhaust smoke on start-up for 10-15 seconds. Usually nothing. Coolant stable on long idles, but after a 30-minute peppy drive yesterday lost almost the entire expansion tank. No visible seepage anywhere. Very little odor if any. Had milky oil weeks ago when I bought it, but I changed it and replaced head bolts, torqueing them twice. Oil showing no return of milkiness. Heater works great, motor runs beautifully. No skips, smooth idle. Turbo gauge shows boost, but no actual boost when driving, despite hooty sound. Pipe from turbo to hooter valve was very loose (not sealed) for a long time. Two small hoses to unit on left firewall were disconnected for a long time. Other vacuum hoses appear dried up. Has a PCV update but not the very latest version. No CEL. Floor under dash shows no dampness. I replaced the spark plugs. Car never overheas. Cooling fan comes on properly. So, WTF is going on?