I did this to my MK1 fiesta cvh about 10 years ago, ran an eaton M62 rootes blower and st3 T3 turbo, the car had 12 psi boost at 1000 rpm running a combined total of 18 psi, had nitrous too, the supercharger was full time belt driven because i could not find an electromagnetic clutch capable of handling the torque to spin the supercharger at the time, removing the supercharger belt showed a peak power increase of 25 bhp on a back to back dyno pull but the gains down low far outweighed the peak losses when the belt was on, I also built the supercharged turbo'd 1.8 focus mentioned beforehand. chris