We have a 91 Montero and I do remember that clicking noise from the dash that would only be between certain rpm's. One day I was in a bad mood and it started making the noise, so I smashed the dash really hard with my fist. It never made the noise since for the last 100,000 miles. It is definately coming from the tac though. there must be something under there that is rotating along with the tac signal from the coil. We also had another kind of clicking noise that was significantly different from the tac noise. This was from the Speedo. This is just an on and off thing, but I never looked into it. both will make noises though from time to time. with 200000 miles on our monty my speedometer probably needs lubrication or something. maybe its getting worn out and noisy. I just turn the radio up louder and i don't hear it.