[PcarDefector]

The 135i is not a great autoX car as the suspension needs a lot of work and it's relatively heavy.

That said, the N55 DCT will be the best choice for autoX. N55 torque curve starts earlier and is more linear.

But the biggest advantage is the DCT. You will get perfect shifts as they will be lightning fast and perfectly rev matched. That means you minimize time losses (compared to manual transmission) due to sloppy shifts and mismatched rpm which both cause unnecessary weight transfer.

Consult the rule book to optimize your 135i for the best class to run in. You do not need engine mods or tune to run in autoX