Have K&N stage 1 filter to start.
Tried Snorkel removal but not happy with hole left in top of air box and risk of stuff falling in. Decided to cut Snorkel down so only entered the air box for about an inch.
Now have to say the difference is not massive but definitely an improvement. Throttle feels snappier and bike running better. For ten minutes work with no cost (if you have a hacksaw) the benefits are great....
Why don't Yamaha do this in first place?