Temp Gauge Fluttering?
 

Hey guys i have a 2000 Civic si, and after i had it dyno tuned on my way home the temp gauge started fluttering.
It never went hot. When im idling or cruising at 2k rpm the temp gauge is fine at normal reading then if i give it any gas at all it will flutter down to Zero.
I have googled this problem and been to a lot of forums and it seems it could be one of a million problems can someone help me out.

And it didnt do this while on the dyno jet. just after when i was driving it home.