heh FRM sleeves are strong as fuck...hence why porsche uses them. You have to get a set of mahle pistons or something with a coating for the sleeves because forged steel is too hard of a surface and will damage the sleeves. but as far as boost goes you can put quite a bit of boost to the frm sleeves wth mahle pistons. just don do it on stock pistons because the cast metal that the h-series pistons are made of are not very strong. g/l with the build.