I'm with you djh65
Everything I have done to my 06 450x was by learning from the people here @ CRFs only. Get your info from people who know what they are talking about. ~ and the others have been through pretty much everything your going to go through... Ask for help & you shall receive
Smog block off kit, Crankcase breather kit, JD Jet Kit 170 main, 48 pilot, CRFs only fuel screw, Twin Air on stock frame with the screen removed, remove the air box snorkel, drilled & installed 4 1"filtered air box vents (Cleaner than cutting up your air box), Pink Wire mod, 49t rear sprocket, Precision Concepts Suspension, complete exhaust system = nothing but fun
All recommendations in steps as I needed them and everything (Except the pipe, a family member hooked me up)was purchased from Ken @ CRFs only. Take your time and have fun with building your bike the way you want it.
Dirk 902