ae86 major lack of power.

[AEugene86]

It just started today, all of a sudden I hear a hissing noise come out of the engine as I accellerate (well I heard it once two days ago and dismissed it) Then it went away only to return. when ever I heard the noise I had no power, I could barely get the car going 50 km/h. Now it seams permanent.
It wouldn't make the noise while idling or downshifting, only when I touch the gas. I think I have a leak in the intake manifold.
anyone else ever have this problem?
any help would be greatly appretiated.

[Deep]

Sounds like a vacuum leak.

[AEugene86]

would that effect my oil pressure, cause it drops and rises rapidly when I give it gas.

[Migs]

sounds like your headgasket has a leak, and very soon, it'll be going KA-BOOM! and you'll see lots of white smoke. Check the rear driver's side corner of the head while you rev the engine

Migs

[AEugene86]

forgot to mention that my cat is going, apparantly its stopping the airflow, that would explain why sometimes I get the HP back, the cat would free up for a while and normal airflow would resume. Just hope that the junk from the cat didn't ruin my new muffler.