Just picked up a used Gryphon

[Jackpine]

I suspect what you felt as surging was the engine hitting the rev limiter between the 2-3 upshift. In a Wide Open Throttle (WOT) shift situation, the shift is commanded at a specific RPM, which you can set in the Custom Options Menu. I would not set this shift point above 5100. (Actually, I like 4975, since the torque and horsepower are generally dropping above 5000.)

Now, as the shift is commanded, the transmission clutch is applied, allowing the engine to freewheel for a short period (until the clutch is released and the shift completes). The freewheeling engine RPM rapidly increases and if it hits the rev limit, spark and fuel is cut to prevent damage. The RPM drops and then the whole cycle repeats until you come off the gas a bit.

If you make sure the rev limit is at least 400 above the highest WOT shift point, this problem will generally not happen. I have my rev limit set at 5500 in the Custom Options Menu. Don't go much above this point either, because the Torque Converter (TC) starts to balloon above 5400 RPM.

By the way, don't set the 3-4 upshift too high. It's actually hard to get a genuine WOT 3-4 upshift unless you're on a racetrack. My shifts are around 4975, 4975, and 4400.