KBFXDLI, you say you didn't like the K&N and went back to the paper element. Can I ask what it was you felt you didn't like? I've run K&N filters in my cars as well as my bike. I'm just taking K&N's word that they are better but honestly I've never been able to feel any difference what so ever. Any gas mileage difference is not noticeable unless you were to test them under strickly controlled conditions. But nobody drives that way. There is just to many variables that will effect mileage. About the only good that I can see is that they will last forever since you can clean them. Like I said, under dyno conditions I'm sure you will see a difference so knowing that some people will feel it's worth the cost.

 

I can identify with Joe with the paper element. When I had my 1200 Sportster, I did Vance & Hines Slip-ons, re-jetted the carb, and installed an SE filter. The bike was a blast to ride, and it sounded good, with solid power and torque. When I installed a K&N element in that filter with THAT combination, I hated it. It sounded horrible, and the bottom end seem to go away. The paper element seemed to have enough restriction to keep the intake noise down, and it ran a little better. You can call me crazy, but a good friend of mine has an 08 FXD and he has opted for the paper element in his S&S filter assembly with S&S pipes. He tried a better flowing element, and did not like the way it responded. I think that there are so many different combinations out there, that one size does not fit all. On my Street Bob, the components that I put together work fabulous.

 

I put V&H ProPipe BP's on and mounted a K&N Factory replacement filter. The bike popped and snorted. Bought a TTS, remapped the ECM and when I started it up I had the paper unit in it to try and make it less lean until I did the tune. The bike sounded quieter and the power that was there was different than I expected. I put the K&N back on and the sound is perfect and the power is very apparent in the seat of my pants when I grab a handful. No more popping and snapping either. Nice to drop a gear coming into a corner and listen to the pipes sing. Gotta love the V&H!!

 

I have it on my bike along with a dynajet kit and after market pipes. My 88 seems to be stronger than most but I haven't had it dyno'd. I don't believe the air filter kit by itself will buy you close to 12hp but it will help some.

 

When I checked out the RK-3910 I noticed that it came with longer spacers. does this mean that I'd have to ride bowlegged on the right side of the bike?

 

It appears that the RK-3910 will stick out farther than your stock unit, due to the velocity stack that is added to this unit. It looks like it is pushed away to gain the clearance for airflow that is designed for it. If it was me, I would buy the Screamin' Eagle piece for your year, install a K&N element if you so desire, and put your cover of choice on it. The contour built in to the SE piece basically does the same thing. I have never looked at any air filter as a way to make more power, just allow the engine to do its job more efficiently, which in turn, will obviously make more power, just not power that you can feel.