My maverick is having a strange problem, it cranks up and idles well. But lacks acceleration and top speed. When I start going it runs sluggish and tops out around 35mph, and when I punch the gas it just bogs down and goes nowhere, it's throwing codes p1171 which I believe is something to do with the fuse box and p1174 which says the fuel is running lean? Any solutions? Should I drain my tank or change spark plugs?