TBIs can't have leaky injectors, they are sitting almost inside the throttle body. No where for the fuel to leak to. One of the two injectors could be a little clogged, or your fuel filter may be a little old. Try running a bottle of Lucas injector cleaner through it and see if it improves. FUel filters are only like $8 so even if it's not that, it's new anyways. Same with the cleaner, even if it doesn't fix it at least you cleaned your injectors a little.
With such a minor issue I doubt a code was thrown, but it wouldn't hurt to check the ECU codes.
If you don't know how, here's the link:
http://www.nissanpathfinders.net/forum/index.php?showtopic=21