the fan delete mod is where you remove the engine fan, replace the thermostat and aux. fan switch with lower temp. units, and put water wetter in your car. what this does is by removing the fan you get rid of the parasitic drag of the fan, so your engine revs easier, and produces more power, and the new thermostat, aux. fan switch, and water wetter ensure that despite the loss of fan, your engine does not over heat.
go to www.bimmerworld.com
for the kit, i think it's liek $50-60.