Steve - What are K&N Filters and what is H11 to H9 Conversion?
K&N is just a drop-in "performance filter". I really dont think you get much performance out of it, but while doing some airbox modifications I went ahead and added one.
The H11 to H9 conversion is a headlight upgraded. I really have not explained it very well on any forum. But it replaces your stock H11 bulbs (1350 lumens) with H9 bulbs (2150 lumens). For around $40.00 you can dramatically increase the output of your headlights. The stock H11 are 55W while the H9 are 65W bulbs (slightly hotter but not enough to do any dmg, as its the same heat output as your highbeams, I have been running this way in multiple cars, I have an impala w/ 85k that has been this way since around 10k). It requires slight modification of the light housing, but its extremely easy. Here are some pictures of the results in another thread I slightly mentioned the modification. I like lights, but I hate illegal HID's that are designed correctly. Any HID put into a headlight designed for Halogen (which includes the halogen projectors on the LTZ or Terrain) is illegal (its not enforced enough imo), but they cause more glare then light on the road. I 100% guarrantee I have more light on the road than anyone that has installed a HID kit, and I did mine for around 40.00 while they spent nearly 200+ for cheap chinese parts sold in a made in germany box (LOL)
http://www.chevyequinoxforum.com/showthread.php?t=11