I've noticed this problem lately.  My tachometer needle will "float".  Let's say I'm at 5K RPMs, it will "wave" back and forth.  It seems to happen at all RPM ranges, and I really see the effect on the e-way.

Any ideas?  

Thanks!

LUBERCATE the tach cable and tighten the cable ends after the lubercation
white lithium greese in a can works good....WD-40 if you have nothing else