in addition to the advice already given, the afr readings going from 10 to 17 quickly may just be that it is way too rich and the sensor can't read that low. sometimes it causes a misfire and shows as being lean, common error made unless you know what is happening.
map sensor is a good call though, if it can't read a vacuum it will just assume full throttle off boost when idling and that will be mega rich compared to what it needs with no throttle or very little.