it should be fine to put it in a 2.5" maf housing as long as you have the tune changed. mine is in a 2.5" housing. it also shouldnt matter where your bov is located in the piping. as long as you have the maf in the straightest part of the pipe you can get. i wish you could get some pics of this thing, lol. here is a pick of mine may be it will help. my bov is between the part before the maf and after the intercooler. it is basically right behind the passenger light.