hi all. my car is running slow after it warms up. no boost after 10 minutes or so . I have ran vcds and im getting ' 17958 -boost control deviation'. from what I have read on other posts, usually it will say positive or negative deviation, as in too much or not enough boost. I have got a price on both map sensor and n75 and they are both roughly £60. but they will not take any returns. so my question is - should I go for the n75 or could it just be the map sensor? I got a feeling its the sensor rather than the valve, as it only ever says deviation, not negative or positive deviation. Please advise .