Bosch VE CSD

[meerkatmag]

Hi, I'm trying to figure out why my 2.5 tdi idle drops when the engine is at very high temp. This only happens when the oil gets up to high 90Cs. If I stop at lights after a long run heavy loaded the oil temp will be high but fine, never seen it get to 100c. The coolant is also fine, sometimes it gets high ish on the dial but nothing crazy. However on stopping the idle drops and the oil pressure therefore drops to alarming levels, sometimes as low as 8psi. Normally it's around 15psi at idle. A tiny bit of throttle will bring the idle up and oil pressure back to normal so I don't think it's oil or oil pump related.

My current idea is it's the bosch VE pump altering timing as it gets hotter, and after a long run the pump gets heat soaked and retards timing causing the low idle.

Does that sound plausible? any other ideas? Or ideas on how to fix it?