I got a k&n air filter and it came with an outerwear prefilter. Would it make much difference in air flow if I do not use it. Just wondering. i am running just a tad rich and I was wondering if that might prevent me from running rich...

 

No, it wont make any difference. But if your running an opened up air box keep the pre-filter on just for water sake. Sounds like you'll have to step down the main jet size.

 

Either way, a K&N will pass dirt and shorten you engine life!