Also you're going to need this!
I'm not sure where to find the calibration kit, but this WILL help your pipe/loudness/power situation. You can keep the stock pipe and remap the bike currently...
http://motocrossactionmag.com/Kawasa...STEM-1481.aspx
OR swap your pipe for this bad boy, however I can't say what kind of power gains if any you make for having a decibel killer.
http://www.btosports.com/p/FMFTIQ
OR if you can have the extra dB(and $$$) I'd opt for this bad boy
http://www.btosports.com/p/PCTI4FSRES
But that's really personal preference. But either way, mufflers touted as quiet in their ads, generally are very quiet in comparison. Also the dB might be measured at idle, and not WOT if that alters your decision.
Suspension - I only found this stuff... The RaceTech kits are sweet, but I thought they came with springs. Factory Connection has springs, but I'd opt for ProAction or ProCircuit springs.
http://www.motosport.com/dirtbike/Fo...rings?limit=60
http://www.motosport.com/dirtbike/pr...KI;KX450F;2010
http://www.motosport.com/dirtbike/pr...KI;KX450F;2010
And attached are the 2 Intermediate Terrain tires I like run in Texas. Like I said previously, we have a fair mix of conditions on each track. These generally work best in harder rock/loose dirt situations. If you can pin down what you ride 75% of the time, get a tire that's optimal for those conditions. Better to compensate for your tires behavior over small areas of land than trying to compensate for greater areas of land.
**Maxxis IT on the right, Dunlop MX51 on the left and used every weekend for about 5 months**