As above really, just fitted a Kenwood sat nav system to my V4 type r, but the speedo does not work!!!!!!!

If i turn the TV headunit off its fine, but with it on the car runs really badly; when i slow/stop the revs drop and has stalled on me a few times!! and the needle will not move..

anybody else had this problem or know what it might be??

just to add;- I have tee'd into the speed sensor wire behind the dials as this is the location of my kmh-mph converter etc.

Any help would be greatly appreciated as i currently have sat nav that i can't use or sat nav and a crappy running car..........

cheers