Emission Systems And Parts

just drove a 92 buick lasabre 3800 and while depressing gas pedal car barely accelerates. notice that the clamp to the exhaust manifold is missing and was wondering if that would cause poor acceleration in that the clamp is gone and compression isn't as it should be. I hear a hissing noise below the power steering housing and am just assuming that when accelerating the exhaust manifold is blowing the air out from where it clamps to the exhaust pipe before it gets to the cat. converter. and it shakes a little while idling but more so when driving. any help would be appreciated. I already checked all the hoses and lines and can't see any signs of air leaking. the noise is coming from below the top corner of the valve cover where it meets the power steering assembly and bracket. the only thing there are some wires going to the injectors and below the PS pulley are the metal lines going to the PS.