It's about time for me to clean my air filter, so i'm goin to buy a spare so I have two filters. I haven't done anything to the jetting of my bike, can I still just throw a uni filter in there or does it breath better than the stock causing a leaner situation. Bike bandit has a uni for 25 bucks.

 

My main filter is a Uni but when cleaning time comes, I just run the stock one for a day or two until the Uni is properly cleaned/dried/soaked, etc. For me it has caused no issues. Maybe the reverse situation is true as well.

Don't know how this all fits in with your conditions or riding style, but I hope it helps.