Loud backfire from the intake, engine stalls, rough idle

Hey guys,
Long time reader, never posted.

I'm handy with a wrench and prefer to do all of my own maintenance on any bike or car that I own- you guys on here have saved my ass a few times without realizing it.

So, to get to the reason that I'm now posting instead of just reading.

Starting a few days ago, I was experiencing my bike running rougher than normal. I work a lot and hadn't really had time to stop and look into the reason. Two days ago, I stopped by advance on my way home from work (needed power steering fluid for a little job on my minivan), and when I tried starting my Kingpin, there was a tremendous backfire through my intake, and then it took a few attempts to get my engine running before I was able to head home. Fortunately, I was right down the road from my house and I made it without any issues. Now, after I finished working on the van, I tried to start the bike again. It was running extremely rough, and I knew that I was about due for a plug change anyhow, so I decided to pull one out and see how they looked. Both were fouled and I replaced both. Afterward, my bike ran a little smoother, but definitely wasn't normal. I didn't have a whole lot of time to work on it, so I had to just deal with it.

My bike is my daily rider, so I dont always have time to pull it apart in detail and work on it.

The next day I again had only a little time to work on it. I knew that I was also way overdue for an air filter cleaning, so I pulled off my K&N and cleaned it, left it out to dry, then resprayed and reinstalled it. Again, running a little better, but still not normal. One major difference here is that when I pull back the idle lever, it GREATLY increases my RPM where it used to just gentle raise my idle- to the point where I've forgotten it was on.

Now, with a clean filter and new plugs, the bike is running great for midrange speeds, and still a little rough on idle. On my way home, however, I realized that It's really struggling to hit speeds that would normally be cake for it. Anything above 80mph feels like I'm asking a lot of my bike right now. When I pulled in to my drive way, I have it an obligatory vroom vroom rev to let my wife and kids (and neighbors) know I was home. When I did this, there again was a huge backfire from the intake and the engine stalled again.

Based on the way my engine is feeling, and the lean smell of gas I noticed after the misfires, I'm assuming I'm having an issue with air:fuel. Now, whether its an air leak or something faulty electronically, I don't know. I'm going to wind up take unnecessary steps in figuring this out if I go it alone, so I'm asking anyone if there is something I should check out before anything else.

Thanks in advance, guys.