P0171,P0174 has me stumped

So I just bought this car a month ago and overall it has been great. 2004 bmw 110k miles, serviced by import dealer its whole life, very well maintained. When I bought the car she told me it had a CES light for the mass air flow sensor. So I think she had it diagnosed by someone who found that out. I have been checking for vacuum leaks the past couple days, and havent came out with anything. I havent taken the DISA apart yet, though. The only only problem related to the code is when I cold start it in the mourning it starts fine, goes into high idle, falls back down, then revs back down. Whole time it starts misfiring really bad. It has been getting down to 18 in indiana and its getting worse the colder it gets. I was going to change my valve cover and plugs this weekend. is there anything I could look at in the vanos? Should I look at just replacing the MAF? OEM? any advice is appreciated guys.