97 993 TT, which I have owned for 4 yrs...bought the car with 44K miles and have faithfully had usual and customary service....pushing towards 75K miles...have a lightened flywheel with a GT 3 RS clutch and muffler by-pass pipes...having ECU upgrade installed this week...supposed to up HP to around 470...I am a little suspicious of that number but that is what Patrick Motorsports is claiming(I do hope it is true...may get a dyno)...little nervous about pushing what may be a tired motor...Is it time for a re-build?...I have been in a 930S when the motor let go...YIKES!!!!...just had a chance to buy a factory new 993TT engine for $17.5K..probably should have done that...I will post next week when the new ECU upgrade is installed...just hope I don't get any fault codes...Steve C 97 993TT(Black/Black)...Portland,OR

 

My understanding is that while there is no magic number, 125k miles is considered a good time to start thinking about having the engine refreshed. I think your question has probably already been addressed multiple times over on the technical forums at Pelican Parts. http://forums.pelicanparts.com/ As you probably know, Pelican is basically the gathering place for air cooled guys.