Recently bought a built transmission don't want to name any one. Issue I'm running into is under stock file it runs fine but when tuned (tried 3 different custom tunes by different people) at wide open throttle I will try to make the 3rd to 5th shift and it will shift for a second then kick me out of 5th and back into 3rd gear. It will do the same on the 5th to 6th shift will drop me into 3rd gear. If I let out of the pedal it will hang in the gear tell I give any throttle then it will drop down into gear. Then if I ease on the pedal after a few seconds it will kick up into the gear. All gears will pull fine when I'm in them. And tq locks up great. I've spoken with the builder but getting other advice also. There are no codes present checked it after about 3 or 4 times with a solus. Thanks in advance for any ideas.