First, you need to get that IAC bolt fixed. That bolt is a M4 x 0.7, probably about 12mm long. You'll need to extract it and replace it or you'll have a small amount of play in the IAC that may affect its operation. Secondly, to clean it, you'll need to take it out, and spray it down with some Brake Cleaner and use a soft brush or soft toothbrush to scrub it down. Keep spraying it with the brake cleaner to wash away the carbon build up. When you got it all clean, use a small drop of oil on the base of the pintle to lubricate it since the cleaner will remove all oils and such.
Its not wise to ever push or pull on the IAC plunger/pintle as it is a low torque electronic stepper motor that does not take kindly to such things. The hissing sound you are here, while it could be a vacuum leak as mentioned, it could also be from the IAC not operating correctly. Its very possible that the IAC may now be ruined. You can always take it back out, leave it plugged in and start the engine and see if it moves in and out, though that may not be a conclusive test, but it will let you know if its completely dead or maybe not retracting or extending fully.
Next, get you some CRC Electronic Part cleaner from Autozone. Remove the MAF. It uses security torx bits that are also M4 x 0.7, so you will need a security torx bit driver to remove them. Once you have the MAF out, spray the MAF element down with the cleaner and let it dry thoroughly. Then re-install the MAF and see if that makes any difference.
With regards to the misfires, if your MAF is malfunctioning, I would expect misfires. As when the MAF fails the PCM is likely relying on other sensors to compensate that probably are not as accurate nor as quick to respond to air flow changes as is the MAF.
Hopefully this helps out some. Let us know how it goes. Sometimes it takes time to diagnose and troubleshoot things on line, but we will do all we can to help keep you from having to take it to the shop.
