The 3.3 is a great engine. it's almost identical to the 3.0 which I had about 350,000 mi. on before replacing in my pathfinder.
There are a few things you can do to wake up the 3.3 during a rebuild.
one of them being, putting larger cams in. When nissan went from the 3.0 to the 3.3 they also went to a smaller cam. When I rebuilt my engine I ended up putting a 3.3 in it with a 3.0 cam, but there are other more powerful cams available. I just had the 3.0 cams already.
Also, the exhaust on the 3.3 is WAY smaller than what came on the 3.0, having the exhaust reran with a larger diamerter tubing does help as well as putting headers on it if you can find some CA legal ones. (or if you don't need to worry about smog for some reason, get the Doug thorley Headers.
Also what sie tires are you running? a regear may be in order.