I have these 3 codes 16891,17705,17544. From searching on here it seems it could be a vacuum leak. Is there other things that can cause these codes, like maf sensor or something else? I replaced the kind of breather/valve thing at the back of the engine as there was a definite leak there. Engine is a BFB 1.8t. Tried spraying pipes but can't find a leak. Also idle is a bit lumpy and when revved, it's slow to come back down to normal idle, even when engine is fully warmed up. I also think it's heavier on petrol lately??