K&N Filter shape/size question - what's the difference?!?!?

Hiya folks.
I've had quite a play with the seach function but didn't quite find the answer I was looking for. I've got a 2002 ZX9R with a yoshi pipe and stock air filter. Since it runs a little rich when set per the factory manual, I'm thinking a less wheezy air filter might sort things out and maybe make it a bit crisper in the throttle response.
Anyway, I see at the knfilters.com website there are two K&N filters for the '9R.


The only obvious difference I can see between the two is the cross sectional area/shape of the filter (and possibly the filter medium - but nowhere can I see this stipulated). The filter in the top picture (KA-0021) is more expensive than the filter in the lower picture (KA-9098).
Questions:
1. Which is the higher performance filter. The blurbs don't give any kind of clue. ??
2. Does the shape make a big difference?
3. I see in my searches that someone recommended keeping the stocker and removing the mesh - how does this improve the filter?
Appreciate your help, thoughts and/or advice.
Cheers folks.
Rob
I've had quite a play with the seach function but didn't quite find the answer I was looking for. I've got a 2002 ZX9R with a yoshi pipe and stock air filter. Since it runs a little rich when set per the factory manual, I'm thinking a less wheezy air filter might sort things out and maybe make it a bit crisper in the throttle response.
Anyway, I see at the knfilters.com website there are two K&N filters for the '9R.


The only obvious difference I can see between the two is the cross sectional area/shape of the filter (and possibly the filter medium - but nowhere can I see this stipulated). The filter in the top picture (KA-0021) is more expensive than the filter in the lower picture (KA-9098).
Questions:
1. Which is the higher performance filter. The blurbs don't give any kind of clue. ??
2. Does the shape make a big difference?
3. I see in my searches that someone recommended keeping the stocker and removing the mesh - how does this improve the filter?
Appreciate your help, thoughts and/or advice.
Cheers folks.
Rob