Newbee question: How does the auto tranny on 2001 540i behave in the "manual" mode if you hit the red line? Does it stay in the same gear until you upshift by pushing the lever or does it upshift automatically?

When in Step mode, the transmission will auto upshift just before the redline. And if you hit the kick down switch at WOT and the computer deems a lower gear usable, it will downshift. So it is only a pseudo manual mode.

The Dinan transmission software changes things to make it more manual. The automatic upshifts are eliminated unless the kick down switch is hit.

The Dinan transmission software changes things to make it more manual. The automatic upshifts are eliminated unless the kick down switch is hit.
I see... But what is an estimated price of such a firmware upgrade? Is it like $200 or more like $2000?

more like 800 or so... u can look at the dinan website