Tach coding plug question

[kalib0y]

yeah the older tachs dont have coding plugs. If I may add a question. Would an E30 M3 coding plug work if I have the e30 m3 cluster? Right now I am using the 325 plug with the M3 tach so my RPMs are about 500 off

[Matt-B]

I dont think your cluster has a coding plug, so i think you need a new cluster also...

my 84 had no coding plug, it was "built in" if i remember right

[highoutput]

I know this has obviously been covered, but i wanted to ask directly for clarity.

I swaped an M50 into my '84 318i and the tach is off,....big suprise.
I've read that I just need to get a coding plug from a 325i and "plug it in".

THEN, I read somewhere that you have to have an '87 and up tach for that to work

So can someone give me the real info please?
My tach goes up to 7k, but I don't want to get a 325i coding plug and find out I really need a whole new tach.

Thanks for any help