OK, then the pipe alone might need a little tweaking on the jets, but you would be much better off doing the usual mods that we all do to really wake up the best. In short, these are open the airbox, remove the backfire screen and get a TwinAir Powerflo filter:
http://www.crfsonly.com/catalog/product ... 260caa490f
If you get the JD jetting kit, it makes things very easy if you aren't into jetting:
http://www.crfsonly.com/catalog/product ... 260caa490f
The alternative is to use Skoot22's NCVS needle and jetting setup. You can PM him for more info.
You don't indicate where you are in the world, but if you are in California, then you have the smog setup which you can remove using a block off kit or plug using Skoot22's method. Read the first 4 messages in the 450X forum and you will gather a great deal of knowledge about your machine.
You will need to replace the fuel screw with something like this:
http://www.crfsonly.com/catalog/product ... 0e412f6d78
That will get your machine running better and cooler. It will also take advantage of your new exhaust. Be sure to set your race sag.
Joe
'05 CRF450X,McClain suspension, Cycra Probends, Pastrana FMX Pro Tapers,BRP Sub mount & Scotts stabilizer.See carb sticky for more