switching to an electric water pump
I know older cars this was a pretty easy and efficient mod to cut parasitic losses and I would never actually do this given I have no skill and if possible even the cost would be high, but in general is this a feasible "mod" if cost were not a factor? It used to be quite easy in a bit older cars and a great way to free up pretty good chunk of power, just like a pulley essentially does.
Still bugs me that the n52 engine came with an electric water pump but it never filtered down to other engines. An s65 with an electric water pump, coupled with its alternator that is not engaged during accel. and the a/c that disengages under heavy throttle, the parastic losses would have been next to nothing