Hi Martin
I got my cat bypass + new 45mm headers from
www.spareshack.com.
They do a type 1 - 45mm headers + cat bypass £356 and a type 2 - cat bypass only £237.
I havent had it dyno`d yet to see what the gain is yet but i can feel a huge difference in the torque and some top end, it has also smoothed it out alot at low speeds (around town etc.) I dont know what the difference will be with a std can as i have termis on mine. You can see how it has tidied things up on my avtar.