Maybe I did something wrong but here are my results 2003 raptor:

1. Ran bike stock.
2. Ran bike with air box lid off, stock filter, big gains on bottom end.
3. Ran bike with stock filter no snorkle and 2 x 1 3/4 inch holes in air box lid, same performance as #2 and #4.
4. Ran bike with Pro flo filter and adapter no air box lid SAME performance as #2 and #3.

I think I wasted $150 bucks on this filter, I believe the stock airbox filter with the #3 set up works great and costs zip.

Next mod is a full Yosh system this week so I will rerun with the air filter choices and post then. For now I would say unless you are concerned that the stock filter does not seal well enough ( as some do ) save your money!

 

Unless an 03 Raptor is different than an 02, how did you take the lid off and have positive retention of the stock air filter in the airbox????? That stock filter sucks with the foam element providing a seal. For that reason alone, the pro design is way better than stock.

 

The reason you can't tell a difference between 2-4 is because you are running the stock pipe. I assume you are running the stock pipe since you are talking about adding the Yosh.

Right now, your power is limited by how much air you can get OUT of the engine. Once you get that fixed with the Yosh pipe you will be limited by how much air you can get IN the engine.

Then you will be able to see a difference in the open air box makes.

RR1

 

Koz:

Just took the lid off and made a couple runs with the bottom lip and gravity holding the filter in.

 

LOL!
Anyway, any engine requires 2 things too make maximum power. AIR and FUEL at right around a ratio of 12.7/1 (depending on engine design). When you introduce more of one and do not compensate by increasing the other, then maximum power is not attained. The pro-flo is a poorly designed, turbulence nightmare though.
Gary

 

Maybe i missread what u posted.. but doesnt sound like you have adjusted your jets?? if u havent of course its not going to make a differnce cut away the airbox and just leave small strips for mounting brackets and jet your carbs and get a pipe youve gotta realize the engine has to breath the more it can breath the better it will run but theres a condition you also have to exhale your breath thats where a pipe comes in handy get your pipe jet it up correctly and youll be surprised by the differnce

 

A couple of the biggest reasons for the ProFlow is a better sealing filter (stock is a joke) and you can run with the lid off.

 

and.. u can cut up the aribox and it will still stay seated.

 

not by itself

 

I never changed the jets as I am at 3000ft so I figured the lid off sinerio would be more efficient than stock and as the machine is jetted for sea level this would be about right. The point I am making and taking into account the comments on the stock pipe is that the pro flo offered no more gain than a stock airbox with 2 holes cut in it.