I have read also with regard to coming out of gear; but it seemed as if most was with TT kit moreso...
On one of my cases i had only removed the detent ball, and it never jumped out of gear.
The case I'm running now, I just did 6.5 w/ rockrat's twin sticks and HD front output, and again, no issues...
Not sure why it is happening when you add throttle; I'm sure you checked for tunnel clearance---have you run it w/o the t-case shift boot on it?
how about pulling the t-case shifter and watching to see if the rails are moving?
Try a call to trail Tough?