Idle hunting

Question

I have an alfa romeo 156 with a bosch throttle body and ecu. When at idle the revs will fluctuate around the idle speed of 1000rpm some times stabalising at incorrect speeds, some times continuously rising and falling. I've read of similar problems in older bosch units but the fix refered to adjustments made that mine will not allow, various screws and such absent presumably because mine is a little newer. Can you help me?