Evening boys and girls. In need of some real help before i lose it. Noticed about a month ago that the cars dropping revs between 400 and 900 rpm when coming out of gear, the revs will drop then come back up to 900 and idle like normal. So far ive fitted new MAF, IAT sensor, N75, all boost and vac lines are silicone, TB reset, cars idling at 20inhg so no vac leaks. Thing is the cars driving amazing, made 235 bhp the other day (vag com 188.7 g/s). Only fault codes have been MAF, thats been replaced today and the Lambda sensor when logging on Saturday but it hasn't come back since. Can a faulty Lambda cause the revs to drop, heard it can cause bad idle, also my mpg is around 25 when it used to be high 20's to low 30's. Someone help .