they dont have a waste gate they have boost bypass but it shouldnt hiss unless theres a vacuum leak somewhere the only time mine hissed like that was when the hose to the egr transducer melted on the back of the intake, my fuel pressure regulator sticks sometimes and it hesitates and its not very often but its done it for a few years now ,when i can feel the pressure regulator start working and it starts pulling harder but thats mostly before it warms up