One thing after another

hi guys, i posted a problem i was getting on here the a few weeks back about getting a high pitch hissing when hitting high boost and had some quick help from Chris Wilson saying it was due to a poor seal on one of the hoses to my intercooler, so ive sorted that out and it has run fine for the last two weeks, my boost controller has two setting LOW (14psi cut off) and HIGH (18.5psi cut off) in the low settings it fine all the way to 7000rpm but if you put it in high mode you change gear at anypoint once past 4500rpm and the dumpvalve goes off but also another high pitch noise like air escaping, ive checked all the joints and cant see anywhere it can be, is there anything else this could be?????