e30 rev needle

[dubman 39]

I have an e30 316, the previous owners put in a new cluster so it has a rev counter, instead of a giant clock. The needle egts stuck on the motorway when i'm doing 80-12..i mean 100 . It hangs around the 2.5k to 3k region, although im sure the engine's doing less by the sound of the engine. Any ideas? cheers