this morning my car sounded fine an ran fine, went to work parked, ok so later on in the day.. here is when the problem starts, i leave work.. get on the freeway and all of a sudden i hear my car making this hissing sound everytime i gas'd it, first thought that came to my mind was... i caught a plastic bag under my car or something, well... pulled over checked nothing anywhere, then i thought it was my intake pulled that off.. rev'd my car a bit, still was there.. so i was like maybe it might just got away, i drive home about 10-15 mins later my car starts to make that hissing louder, i was in 4th gear i downshift into 3rd to slow down and when i barely tapped the gas the hiss was just way too loud... any ideas? i tried to guess as much as possible... but no luck.. help please? thanks.

oh yeah my car is a 96 honda civic dx d16y7. stock everything.