That hissing noise you heard has nothing to do with the codes you posted.
The conditions you described mean that there is unmetered air going through the system. That means you have a vacuum leak somewhere. A can or two of intake clener spary, sprayed on the intake and vacuum lines, will aid in pinpointing it.
I ordered the parts a few days ago to perform an intake rebuild on the wife's car. Exact same codes but runs fine. The spray indicates a leak in the infamous intake gaskets.
Probably start mine Tuesday or Wednesday provided parts arrive on schedule.
Steve
