Gentleman and Ladies if any...

I have been fighting a very strange problem with the car. It will run 120MPH a few runs and then 116MPH. At either MPH it is stupid consistent but does pickup ET when it runs the higher MPH.

Only place it shows in graphs is Engine RPM, driveshafts overlay perfect.

graphs. Top Engine RPM, middle trans pressure, and bottom is driveshaft. Pressure are all within 4-7psi - carb, oil, engine temps and trans temp all within 3-8 degrees.
https://photos.app.goo.gl/CdJWrKEmWYnSMHms6

logbook
https://photos.app.goo.gl/hFqMp7irc8bv7pLB6

final run at 120mph
https://photos.app.goo.gl/e4QdBF54EtBXuWnp9

I put a new grid in it last year, zero difference and went to the finals of a race. I have changed carbs, on alky with mechanical pump, FP all good. AFR looks about the same. brakes are TBM and are not excessively hot after a run vs 120mph.

I ordered a new crank trigger and harness that I will install this week, along with new coil.. The wires and plugs have also been changed. Distributor, rotor, converter was even swapped last year. Third member broke two weekends ago so that is all new and fresh with 9.5Ford. Axle bearings were checked when out and felt good.

It is acting like the timing is retarded or advancing - with timing light its rock steady at 34*. I cleared out the grid memory card. I went thru every table in grid and there are no retards setup. Just the basic stuff. Weather is not a factor either I have Ifamily system and the runs were within 1hour.

Lastly I went thru car and removed every ground wire, cleaned, and put star washers, sprayed them with protector after they were tightened. Did that last year and again this past week after it did this at 5k weekend race in the semis to me.

Does it with BOX and NO Box alike.

Looking for ideas.