Heys guys, i was also racking my brain over this as mine has been doing it for quite some time that now it doesnt even flicker just stays over 9000 dead so i pulled my dash off and pulled the cluster half out and all i did was unscrew the screw just above the right hand black loom (looking at the tacho face on) be careful not to drop the washer and lose it, i was tempted to go get some contact cleaner but for now thought id just wipe it with a clean rag, put it back together and now it was flicking around 4000 so i knew i was on the right track, i found that some of the other screws were a little loose so i tried to do them all up at an even tightness because i found if one was too tight it would flicker even worse, so get them nice and even then i put my cluster back in GENTLY so hopefully i dont bump anything and make it go crazy again, it idled fine so i took it for a drive so far so good, revved to 8k and back still good.
I know this sounds ridiculously simple but thats what has fixed mine im sure everyone might have a more complex problem im just throwing out one solution for now, will update if it plays up again in future.
Bryce.