idling problem

[butlere30]

hello e30 zone members i am new to your site and in need of some help i have a 325 c plate manual with an engine taken from a 325 e plate auto a few other bits were changed on the engine and runs well but the idling is playing up it will be searching for an idle between 5 /700 and if you rev the engine high it will stall or try to i have put a second hand idle valve on that helped for 20 miles and replaced the air flow meter can any one have an answer to this problem many thanks