I thought the most of the people that do a turboII swap go S4 for lower compression? Or maybe they just use S4 rotors...

 

s4 rotors are 8.5:1, s5: 9.0:1 (<turbo only).

While the 8.5 gives a larger room for error as far as tuning goes, the 9.0's will have more preboost torque with a minimal impact on max power.

Otherwise, s5's have hardened stationary gears, some have stronger dowel areas, and they have optimizations to the shape of the rotor itself that are rumored to be worth a few ponies.

I THINK the ports are better on an s5 as well as the rotors being lighter, but don't quote me on those 2. The real reason you want the s5 is the stat. gears.

 

same as a peripheral port except you can run with the other intake ports open, a semi p should explain itself its the size ofe the water jackets or 1inch or slightly bigger sounds nice and runs great.

a friend of mines has the so called fastest 12a turbo 5spd and he has a full bridge with a semi p...ill see if i can get a link to a video but they call him ballamon...