hey while your at it why not get one of those mufflers off ebay that make a spool sound so people will think your twin charged haha. j/p man. i dont know of any way for you to add a REAL blow off valve. with the supercharger like it is...maybe if you had a centrifigual you could put one on but i'm still not sure it would work. i guess it would because your rpms don't shut right down as soon as you let off the gas so it should blow. just not have a purpose. but ya i'm sure they make fake ones for something like what you got but.. i'll just stop lol.