I took the stock filter and cut the inner filter part, the paper cardboard corrugated stuff, cut that out and replace with UniFoam that I purchased from Kymco dealer in San Antonio. UniFoam is stuff that motocross racers use. It's inexpensive, works great, and perhaps the scoot breathes a bit easier. Not sure about that.
A piece of UniFoam large enough to make several filter inserts is about $7.00.
I'm on K&N's email list to notify as soon as they make a filter for Xciting 500. My baby likes to breathe.