i had this idea a few weeks back on the way home from the 'ring.

i have the twin downpipe exhaust and power engineering stainless system and plan to tee (or more like a Y-piece) off a straight pipe from each of the downpipes to exit each side under the front wheelarches. there will be a diverter flap that will either be cable operated (i can see from the picture above that a throttle flap and spring is a good idea) or better still, actuator operated.

was thinking it would be cool to have the normal silenced exhaust when driving on the road sedately, but when you get over 6 psi boost or something it just goes straight through. would help turbo spool up and sound the bollox.