Which Mods and What Jetting?

[bigredisb]

Alright after I ran the 3rd tank of gas through my new 400EX I decided to start modding it. I already ground the welds out of the headers and thats about it. I ordered a EHS racing airbox lid (basically an open airbox). The next choice is between Exhaust or a power up kit with a K&N and a prefilter with a jet kit.
Should I add the air filter before I add exhaust or should I run the stock filter in an open box with a new slip on?

So the next questions would be:
If I run a K&N with a open airbox and stock muffler what would my jetting be?
If I run a open box with a stock airfilter and a Lexx what would the jetting be?

I run between 250ft to 1000ft elevation and do run in the cold quite a bit.

Thanks!

[BigBore24]

if you cant do the mods all at the same time then i would say it is up to you as to which to do first. imo it is 6 one way half dozen the other. if it were me tho i would do the air filter first and not rejet, then do the pipe and rejet. that way you only have to rejet once. i cant help you on the jets since im not stock and cant remember what it shold b. but a lot of people are gonna tell you not to run a k&n filter. i say they are fine as long as you oil them every ride or 2

wait until you have everything before you jet. I had a K&N sitting in the box for 6 months because I didnt have an exhaust yet.

[bigredisb]

I have had the same feeling about the K&N filters. I used to run foam on my last dirt bike and liked it. Who makes a decent drop in faom for the 400EX? Since I will have the airbox lid removed I though I must rejet? Doing the rejet twice is no big deal since all the plastic comes off the machine after every ride. I am a bit touchy about how the machine looks. You could literally eat off any part of my dirt bike.