Hello i was putting in some sea foam when i heard what i thought to be a vacumme leak or something.....so i find the problem....I open up my air filter and i hear a hissing sound.........anyone know the cause of this?

 

i did this before i put in the sea foam so just in case you wondered

 

My 91 SE has always made the hissing/sucking sound from intake opening just behind the drivers side headlight. I can even hear it from inside the car with engine idling and window down.

 

no mine is closer to the MAF or coming from it

 

Loose nut?

 

well, considering your engine is an air pump, i wouldn't be surprised to hear that "sucking" sound coming from your intake.

edit: loose nut.