Rough idle

Hello wondering if anyone can help 

I have a v5 uk turbo 2000 had a full engine rebuild was running fine then had a M.A.F fail and knock sensor fail together swapped them out for new units car ran fine for a few months now the cars idle on cold start veries 1600 - 1000 once warm the revs will drop about 100 - 200 rpm it will stuble but not stall  and again i have replaced the iacv with a new genuine 1 not a knock off i have 3 new mafs genuine tryed all of them with no luck checked all vac lines no leaks also no cel codes and plug a reader in shows nothing i have reset the ecu as well but no luck any ideas/help would be much appreciated thanks ben