Udp's are a decent mod for the v6's. There are a few dyno sheets out there showing that the 25% pulley does offer some gains.
The only time you should consider not running a udp is if you have a large stereo system or plan on supercharging in the future.
I personally wouldn't order from RPM Outlet...I order my exhaust there back in 06 and had a bad experience. I've also heard other negative things regarding the place.
ASP makes the pulley, you could either order from them or check site sponsors...I'm believe CJ Pony Parts and Latemodel Restoration offer them for the 99-04 v6's.
12 Black GT500 SVT PP l 2.6 Pulley/Idler l Airaid l o/r X l 305 NT555R's l Recaros l
04 Azure Blue Mach 1 / 03 Sonic Blue 3.8 / 14 Sterling Grey F150 FX4 402A 5.0 / 11 GT500 R.I.P.