1990 tachometer problems

I have a 1990 Corvette .... Not ZR-1 or anything but for some reason my analog tachometer is not showing the proper numbers... at idle it shows 3000 or more even though a computer shows normal idle... Is there a way to adjust the readout on the dash .... it looks like it is scaling right but it starts at about 3000 and will easily go red line when you step on the gas.... the engine runs correctly but the gage is wrong... any suggestions????

i have a 90 rallysport camaro that is doing the same thing, i took the clear panel off and tried messing with the needle and that didnt work, so im going to get a whole new instrument cluster.