I have a comptech supercharged s2k ( I don't know if anything that has to do with that is making it like that). The speedometer is going crazy and sometimes statying at 0 MPH or just goes crazy on me...
Does anyone know what it may be ?

 

I'm guessing maybe the aftermarket EMS may be affecting that.

 

check for a loose ground bolt on the back of the head. I think there was an old thread on this if I remember.....