I set the Affinity mask as recommended. No fps advantage. I then found that my Orbx Scenery was having difficulty in getting its share of the action and when in complex areas all the 3d scenery was flattened. Pausing the sim allowed the return, bit by bit of the 3d stuff.
Removing the JOBSCHEDULER] Affinity Mask setting from the p3d v4cfg file cleared the problem.