K&N pods are not an effective "upgrade", no performance benefits for time & money. While pods may be effective on bigger bikes because it's not possible to fit 10-gallon airbox and 5-sq-ft filter on 900cc bike, the Ninjette's airflow requirement is so small that stock airbox flows more than enough and presents no restrictions. A 2-1 exhaust would yields tonnes more improvement in power.
Yeah, I had front-end bottoming issues when braking on my '02 when i first got it. Need to stiffen front-end.
1. Shorten spring & replace with PVC spacer. Did this in '80s when selection of alternate springs didn't exist. Local 250 guru docments how here:
https://bayarearidersforum.com/mini/...d.php?t=310628 ... Or
2. Buy replacement springs in 0.75kg/mm rate (ideal for your weight for street riding).
http://sonicsprings.com/catalog/index.php?cPath=29_59
For more spirited riding than just commuting, you'll want to install
Gold Valve Emulators. Use with 10-15 weight oil.