Ok i have a mk5 rs2000 engine in my mk6 saloon, but the rev counter aint working yet as it hasnt been wired in.

Ive been speaking to a lad i know with a mk5 rs2000 conversion in his mk6 escort and says his rev counter is only working half (ie - it says 3k rpm when hes doing 6krpm), hes been told this is due to the zetec have twin coil or summin and the rs having single coil? Any of that true and if so how would i get around it?

Mark