I have a Slk 320 2001 and I was looking at the mods available. I looked at the pulleys and stuff but I figured it only makes power on the supercharged ones like the 230, slk 32. I recently changed my spark plugs, oil and doing most of the maintenance for this vehicle. I was wondering what mods do I add to add some more hp? I also looked at the air filters the k&n one but I've read it doesn't do much hp to your car.