We all know that twisty thing on the right side is nothing more than an on/off switch!

 

If I had spent the money on the fuel pack I would get a better intake.
I went the cheaper route and just use the Xieds and the K+N air filter and didn't change the back plate. I also went a tad bigger with the baffels at 1.75 not getting too far away from the stock ECM capabilities.
Bike runs great, it does have minor popping in the exaust burning the extra fuel slowing down down shifting but very minor. The colder it gets the better it acts.
The K+N filter is washable and worth the investment.
I ride in the rain and it gets wet in there and the stock air filter is paper and you know what happens to paper when it's wet.

 

My stock filter isnt paper. It say to was it.

 

I was unaware that you could wash a stock air filter, maybe something new.

 

I don't believe your popping is coming from "extra fuel". My 2010 FXDC was popping with Xied's and Rush Slash cut slip on's (1.75 baffles). I believe you are still running lean. My popping disappeared once I added a Big Sucker and added more fuel with a Dobeck TFI. The XIED's weren't adding enough fuel once I added the slip ons.

 

You don't "need" it, but engine components should compliment each other. An engine is basically an air pump, so it makes sense to free up the "suction" end as well as the exhaust.