All, This is something that I decided to try out, but certainly don't recommend anyone do. This modification will permanently modify a part of the motorcycle that might be under warrantee . . blah blah blah and so on. That being said, this modification did work for me, and replacing this airbox for resale or whatever should be pretty cheap. Here is a link to the photo gallery that I posted some pictures and comments in . . . or just down below and you'll see the important stuff. Here's a picture of the tool that I used to open up some holes on my airbox. Its use prior to this was opening up holes for various reasons on lexan bodies on my model R/C racking trucks. Its available at hobby stores and etc - be careful - it is VERY sharp. Since just about day one, I've had a K&N stock replacement air filter for my 2011 FXDC. I was tired of the sometimes anemic performance on very hot days, stuck in traffic and etc. Deciding to take matters in to my own hands, I noted that the air cleaner got dirty on on the bottom. I used the pictured lexan auger to open holes along the perimeter of the airbox starting from the top of the airbox all the away around to the rear. If I had it to do all over again, I'd use my drillpress to start the holes and finish off with the auger. The advantage the auger has over the drill is that you'll get a slightly beveled inlet that should minimize/eliminate any whistle. So far I haven't heard a peep from it. I believe that I'm getting a bit better throttle response and that the engine does also reduce RPM quicker as well. I also noticed that instead of the normal 42-44 MPG, I'm now getting nearly 51 MPG (95/1.88 = 50.53!). Those results don't really make any sense to me now . . . but someone else might have a better idea why I'm getting better mileage . . . less restriction - less work? Not sure. Thanks - Mark!