Easy way to get a steel pipe plug out of aluminum intake is use a bernsonatic torch with mapp gas. Get the plug freaking hot and keep chilling it down with WD40 then heating if back up, and chilling it back down. Eventually the WD40 will work down in the threads and a pipe wrench will break it loose and it will thread right out. Use brass or stainless steel plugs to avoid them corroding to the aluminum.