Hi Guys,
I checked the pressure relief valve for correct seating using engineers blue on the plunger and found not to be seating properly. Gave the seat a tweak with the "special tool" and checked again, getting a good wide seat. Replaced the spring (the old one was ok, but changed anyway) and added 2 washers behind the spring. Hey presto, 20PSI at Idle and 30PSI anywhere above that. And now the pressure isn't chasing the throttle as it had been.
Will double check the electric pressure gauge against a new hydraulic gauge I bought before flying at the weekend and report the findings.
Have bought 2 x 2" aluminium flanges and flexi pipe to fit some cold air ducts directed onto the sump as there is no air cooling to the bottom of the engine at all, except the hot air coming down from the cylinders.
Cheers
Gavin