[dparm]

The advantage a TTY fastener provides is that you can use a smaller fastener and achieve the same clamping. It's also important when you need to maintain clamping force throughout a wide temperature range, such as what a transmission might see. Head bolts are TTY because you need them to clamp correctly if the block is ice-cold or very toasty out on track.

My opinion is that BMW chose to use TTY very intentionally here and I would not deviate.