My St170 oil/head temperature rises rapidly upon acelleration in 3rd gear but come down rapidly if I back-off on the acellerator. This car is stock standard since new with 336000km (yes 336000km) on the clock. I need a quick answer to prevent engin damage! The motor performs well when cold but it feels like you go with the handbrake applied when warm. I have replaced the fuelpump, fuel filter, VVT cam oil supply valve - but the symptom persists... HELP!