Pulling my hair out

I set the high side limiter to its max of 10900, and it still had the issue. Tried the two step from 3000 to 4000. Launched from an idle without using the transbrake, and it did the same thing but just once. I’ve had the problem of it porpoising the rear suspension before, and this isn’t it. When it does that it will rev way up, and now falling on its face. When I’ve had that problem I can fix it by tightening the shocks a click or two.
I removed my front shocks, and can’t feel any abnormalities working them in and out by hand. Doesn’t mean they aren’t bad, but not glaringly so.
I really think this ties into the problem I had last year with it triggering the shift box to hit second at the release of the transbrake button. Never could figure that out, so I’ve had to shift by hand. Seems like something in the box is reading actual engine rpm wrong which would trigger the shift box, and now activating the limiter.
I wonder if it is an internal connection inside the box, affected by launch g-forces. You have had problems with the box that you still havent solved.
I would beg,borrow, or steal another box, (hopefully a known good one from a buddy) and try that.
It sounds to me like an ignition problem, not fuel or suspension. My half-fast opinion only.