s10 brake booster removal

here is my question. i have a friend that is trying to remover his stock brake booster on his 94-03 s10, to install a smaller one for dubs. i havent seen it but he is having a problem removing the bolts he got all but one out. and he said that hes tryed every type of tool to remove it. does any one know a trick or what needs to be removed to allow space to get the bolts out. thanks