I got 3.9 gears done last night. I have a Police Cluster in the back somewhere. I had a look at the Speed Calc on the Tech Documents and it says it will show -26.6% inaccuracy.

So is that a simple correct by 26.6% (or as close as possible, maybe 26.5%) on the Calibration mode?

As, is it a simple swap over from GLi cluster to Police cluster?

the signal goes to the cluster then to the ecu...

so i think youll need 2 frequency adjusters....

if you go a diff ratio of 3.7, 3.9 or 4.11 then there is no speedo sender available and youll need a freq conv for the dash.. then youll need another so the ecu can shift right..