e90 320i idle problem vibrating

[bmwdrivingmemad]

hi there im new to site so please bear with me if im not writing in the right section about my e90 bmw
hi im hoping somebody will be able to help with info as the the problem im having with my bmw its a e90 55 reg 320i petrol manual
my problem is on idle (tickover) im getting a vibrating through the car and my rev counter is flucuating beetween 600-700 rpm up and down up and down the vibrating im getting is always there on idle iv changed oil inc enging flush longlife oil plugd all filters iv had new clutch and fly wheel and new cam chain inc all tensioners and chain guide the problem was there b4 i changed all these things and it is still there now the car dosnt seem to lose power only problem is on tickover
2 differant garage cannot tell me what it is the second garage told me his maching pick up a faulty lambda sensor but he deleted the code and said the lambda sensor wouldnt cause this problem im having so i thought id cut my losses and book into bmw thinking theyed tell me straight away well £130 later they tell me the only thing they found was bank 1 running to rich and bank 2 running to lean whatever this means some one please tell me as they wanted to do further compression test and leak and valve timing test but wanted to charge me £517 +vat to do this .
please some one tell me what problem im have if you put ur hand near the back exhaust it fells like pupupuppupuppuppup could this be the lambda sensor or timing what please please help its driving me crazy

[Big Evil]

More like a vac leak, or a failing/failed cyclone separator (aka pcv valve)