I have an 04 pred and my budddy has an 03. We went to woods canyon lake over the past weekend and before he went he installed the Dial-A-Jet system on his pred. My bike (stock) was having some noticable power loss. I had to adjust the throttle to keep it ideling. He had no issues to speak of. One simple adjustment of the Dial-A-Jet and it ran like we were here in phoenix. It takes about and hour to install and costs about $75.00 with the snorkel plus s&h.
Here is a link to their web site.
http://www.thunderproducts.com/dial_a_jet.htm