Airfilter/Arrestor Mod.

I have ordered the K&N filter for the Honda and I plan on running the bike this weekend in WV without the spark arrestor. I have a couple of questions. One is, when I get the filter, I have been told that If I dont spend the extra 25.00 on the "Pre-filter" I will have to oil the filter myself. Is that true or do they come allready oiled and the "pre-filter" is just an extra...If I do have to get the "Pre-filter", I have heard that I can use Stocking or Panty hose in place of the "Pre-filter" from K&N...has anyone heard of this? The next question has to do with a possible lean condition. Will I be running lean with the new filter and the spark arrestor out? I know that the Foreman 500 TM/FM/ES all come with a stock 162.5 jet from the factory...which seems large to me and I think has to do with the wheelers design being for heavy duty farm and utility use. Im not too worried about running lean but wanted to know what you folks thought. I was also wondering what kind of power increase you might see form a filter change.

Thanx.

J.