GS Paralever arm - raises rear by about an inch or so, makes steering much more responsive and quicker. Highly recommended mod.
Laser full system/chip - mainly for the looks and noise, but although not giving a huge power boost it definitely makes the motor more lively. Possibly a few more vibes but not so much as to make me change back to standard. Laser cans can be easily swapped with the OEM ones for quietness/winter etc etc.
Boxer Performance (Lennie's) carbon induct - whilst not denying the quite wonderful effect this has on the engine's upper rev range (5k plus) I'm not sure that it doesn't kill a bit of lower end torque. Still recommended though as it gives the motor a real lease of life at the top end.
Ohlins shocks.
Ilmberger hugger - arguably the best on on the market. Does the job and looks pretty damn neat too.
