sounds like a cylinder is not firing.even if it had a boost leak you wouldnt hear massive noises from the valve cover.you need to take the valve cover off,look at the lifters and see if any are broke.(it happens and it runs really shitty),if you see that everything is ok take a compression test,sounds to me like it is a internal problem.i alawys blew my i/c piping off and it ran it would idle just wouldnt go any where near boost.but that could of been the massive fuel my car was gettin lol..