EGT guage freaking out
 

i installed my EGT and oil temp guages last week and everything has been fine, until yesterday.
yesterday i was driving with my parking lights on, and glanced at the EGT and it was fluttering all over the place, i thought it was a bit strange, so i pulled over, shut the car off and all was normal..start it back up and unconsciously leave my parking lights off and notice it didnt do it again..so today i'm driving home from work (its dark) and it starts freaking out again..so i shut the lights off and all was well...what gives?
i have my oil temp guage hooked up to the same power source for the light as the EGT, the power for the guages is coming from my cruise control switch (ign switched), the power for the lights is coming from my foglight switch (parking light switched). oil temp guage doesnt work too well (sensor location gets alot of wind and cools it off apparently) but it works if i'm sitting somewhere, it'll get a reading at stop lights and at very slow speeds, but otherwise its useless to me (yes i'll move the sensor soon).
why is my brand new autometer EGT guage freaking out with the lights on?

edit: there was no splicing between the EGT probe and the guage.

have you tryed a diferent power sorce for the gauge

if you move the power to somthing else and it still does it the gauge is prbobly the culprit

where did you locate the probe and what reading are you getting when it works

whats it grounded to?

there is a bolt that holds the seatbelt on, its grounded to that, its right behind the pillar.

its wierd because it just started yesterday when it was raining (but that shouldnt affect it, all the power/ground is inside the car).
the power and ground for the guage lighting shouldnt affect the guage readings..its so strange. the guage needle moves around very quickely like its getting fluctuating voltage from the sensor, but it shouldnt be because its on a different power source than the bulb.
when the EGT guage is working, it reads 0 when its cold, all the way up to 1300 when i'm gassin' it through gears..idle is about 800, cruising is around 1000-1200 depending on situation. i drilled into the front exhaust manifold and welded the bung into the hole, no leaks or anything...it SHOULDNT be the guage because its only affected when the lights are on.
i do have a big bundle of wires stuffed behind the pillar, should i shorten everything? could it be interference between the wires like alternator whine in a stereo?