You would need someone with the right kit to measure cylinder head temp'. It's normal to run rear pots slightly rich to keep them cooler when doing custom maps. However, I do not think this is the cause in your case. I am sure you have either air or water in the fluid. Brakes are simple....they really are and so are the causes of them being broken.

Cheers M8. I'll start by flushing the rear brakes through completly with new fluid.

Craig

I've had me 998 boil up it's rear fluid a time or two, I do tend to use the rear brake quite a bit.

A fluid change could well cure it, if the fluid is old it boils more easily as it's hydroscopic and the increased water content lowers its boiling point.

Brake fluids have a dry and wet boiling point. The wet is usually a lot lower, in some cases an couple of hundred of degrees lower.

Ray.