http://www.wortec.co.uk/uk/Video_Pages/Video_fourinch_switchable.html

 

 

would it be possible to have this fitted to a turbo car, would you gai or lose power?

That car probably has a remote bypass valve which is the key to stationary sound changes. This exhaust company makes them for exotics as well as for certain BMs, if you watch 2.05 into this video it explains how it works.

I have one my self (not on my Z), and at a stand still i have one kind of sound and with a switch adjustment the sound changes drastically. Though i dont usually do it at a stand still because there is no benefits to doing this. The bypass valve will automatically open as the car drives at over 4,500rpm on the road. So bellow 4,500rpm the car uses just two exhaust tail pipes, above it uses all four. This increases the cars power and changes the sound. You can adjust when the valve opens at what ever rpm by the controll box.

Hope you understand and it makes sense.