My 533i idles at 1500 rpms once it is warmed up. Are there any other things that can cause this other than the slider valve and/or idle control brain box?

three questions
1] have you replace the valve & C.U. with KNOWN
GOOD ones?
2] does the speed change cold to hot ?
3] does it 'hunt' [ speed goes up & down ] ?
whoops ! ! one more....
4] any other symptoms ?