Can't comment on the diesel care one, I have fitted an iDrive one to my BT50 and it makes a big difference to the lag when taking off from a standstill. I know there are sceptics on this forum that say just push the pedal harder but for me the iDrive is worth the $245.00.
FYI I set the iDrive in U3. It has auto, economy or ultimate settings, (ultimate 1 through to 9).