IAC sensor question

Last week I replaced the IAC valve sensor on my 2002 Pontiac Grand Am GT 3.4L 6cyl. It was reading a P0507 trouble code (rpm high). Now I'm having trouble with cylinder misfires (previous post) and the diagnostic test is also reading P0506 (rpm low) along with the cylinder misfire issues. Isn't the IAC valve sensor just one sensor...meaning there isnt one to replace for rpm high and a diff one for rpm low? Could my cylinder issues be causing this code and its not really a problem with the IAC? Like I said, I JUST replaced it last week and for months the car has not started by just turning the ignition, I'd have to tap the gas to get it to run. As soon as I replaced the IAC sensor it starts up like normal so I dont see how I would have to replace it again already. Please help.

See my post on the other thread, you need professional on site help with this.