Okay so the thing we had done prior to the shop was check all the ground we could find and got new crank sensor cam sensor aicv vanos and it still did it after the shop tried a couple dmes to see if that would fix the problem no changes appeared
but in the past wile he drove it it would just randomly fully work like full rev range and then just cut out back to where it was so thats what leads me to someone butcher job on the auto harness look tbh im not to familiar with bmw but i have done some ls400/sc400 manual swaps and I really cant imagine its going to be to difficult to spot the issue with it but on the pre obd2 bmw that where auto if it was in “park” is there a set rev limiter for park as opposed to “nutral”