I spoke to a kymco dealer about this as trying to wring more out of our super 8 50t, and they said they tried allsorts of various aftermarket filters and jets etc with them, but ended up going back to the origional air box as worked best all round.
Have you tried fitting an 82 or 85 jet with the standard box, we are about to fit the 82 for now as couldn`t get the 85, also about to do the cdi snip which sounds as if it really helps.
Whats it like for hills etc where you are as we are popping in 4.7 gram rollers this week, a scooter tuning place told us for cost value lighter rollers add the best boost.
If not too hilly where you are 5 grams would be about right I hear.
Its all one long learning curve trying to get the best out of the 4t engine.
I was told they actually run far better once the cdi is done so the revs less limited by a Kymco dealer when I ordered the jet( and on here thanks) and they actually run where they are supposed to and better. Maybe even better MPG too.
I was also told they are only run in at about 4000 miles and then go far better !!!! so we still have around a 1000 to go on ours.
We also just bought the right Iridium NGK spark plug CR7HIX does a larger better spark which should help staring and running and fuel etc, also it says on the NGK site they need less electric charge so good news on the cdi snip as you get to the higher revs the charge reduces a bit so if less is needed for these plugs to still do a top spark all for the good.
I`d give them a go, same in the agility as the super 8, same engine I believe, I`ll get back once it gets here in the post and goes in.
Good luck etc.
Best Mark.