MSD distributor issues

My Duster race car is having what feels like a high RPM miss. The car usually pulls hard to 6500 RPM but it is now flattening out at about 5800. ET has gone from 12.4 to 13.0 with MPH going from about 110 to about 104.

There is visible rust on the MSD distributor magnetic pick up but none on the 8 fin reel.

Runs and starts great like always driving around the pits. Engine sounds great with no funny noises or anything. Timing verified as 35 degrees total - where it is has always been.

Plugs look good.

I have already replaced the fuel pump and filter with no effect - fuel pressure a steady 7 psi.

Anybody have similar problems or other ideas?