''Sticky'' RPM guage Options

[dudeofchaos]

I took the car out after a few months of storage. Everything's fine but the RPM guage seems to be ''sticky''. At first it didn't go any higher than 1500rpm, then when I gave it some gas it went up to 2500rpm. Now it goes up to about 4000rpm but not much higher. When I rev harder, the needle just stays at around 4000. It seems like it ''frees'' itself when I give it quite some gas. I could try revving really hard and see if it fully unjams but my guess is that maybe the sensor is clogged or dirty.
Anyone knows where this sensor could be so I can clean it?
Thanks.

(It's a Gt-Four.)

[trdproven]

might not be related but ive seen a few times when cars don't run for awhile or the gauge cluster has not been used for a while it would get sticky or less movement. i've also seen over-revving break a cluster, and i thought it was the sensor but when i tried another cluster, it went back to normal. IDK, swapping out another cluster to test from a friend or something seems easier and less drastic if you have a spare or access to one.