Maybe it's just me, but I didn't see anything on that website about how to increase power in a VG. To the OP, I recommend searching the 3.3 swap or if you like some good reading, try this....
http://www.nissanpathfinders.net/forum/topic/28728-project-pathfinder/
A member here bought this rig not to long ago and is active, I just can't remember what the screen name is at the moment.
Loss of power can be from many things. You may want to state the year of your rig, how many miles you have, what mods have been done and what kind of maintenance has been performed. Several members have woke their rigs up with a simple tune up and decarboning. From there you need to help it breath(intake and exhaust). Maybe I went a bit far with what you were asking for, but hopefully I gave some useful information!