You didn't swap in an instrument cluster for a 6 at the same time you replaced your 4 with a 6, did you? The 4 cylinder cluster will work, but it won't read correctly. You need a 6 cylinder cluster. Also, it sounds like your connections on the IC are loose.
Quotes to live by:
guessing gets expensive
nothing is more expensive than a cheap BMW
buying a ratty example (of a BMW) is a parasitic relationship.(and you ain't the mosquito)
Ken Kanne, Silverhill, AL, E36 Forum Mod/Craigslist addict/Hoarder of all sorts of stuff
1995 318is "Bebe"; 1993 325is "Elvira"; 1985 635CSi "Katja"; 1984 633CSi "Sylvia"; 1987 325is "Odette"