99 SL2 Speedometer 20mph faster than car

[gostmn26]

I just had the car inspected and the mechanic had to replace the check engine light. When I picked the car up the speedometer is running 20mph faster than the car all of a sudden. It only goes down as far as 20 mph and rests there when the car is parked.

I know the tires are the right size, I have also just put a new CPS in it along with a new Secondary Air System. Don't know if these mean anything or not.

I am thinking VSS but am leaning more towards the instrument cluster as he replaced the bulb and it was fine before that. Could he have damaged the cluster somehow?