I changed the broke plug and can still hear a hissing sound coming from the engine compartment and also at slower speeds I can hear a rubbing type sound. Could there be a crack in the brake booster line that was opened when I removed it to seafoam it. And if so, could a small leak in that line cause the brakes to not release? I did notice that when I drove it yesterday that the brakes didnt seem to stop as fast. Thanks.[/align]

 

Sounds like a possible vacuum leak. Check the hose that you unplugged for cracks or possible hole. A vacuum leak would effect your stopping force.