Hi have above car in at moment and keeps flagging code 2745 multiplication mixture adaption.Will clear but returns after a couple of days.Picked up car earlier and drove hard back to workshop.When pulled in to check,emmision light went out on own.Started to check car for air leaks etc,none found,but do have considerable vacuum on breather pipe to rocker box(pulls your finger into hose with force).Does anyone know if this is normal amount of vacuum for this engine type.It holds oil cap on with considerable force if you try to remove and makes a sucking noise if you pull dipstick.Any advice anyone....