As far as a performance chip the only route that you can really take there at the moment would be a JWT ecu. Those cheap chips they sell on ebay are usually a joke but even more important, the stock VE ecu doesn't even have an EPROM chip to replace. Another decent route, that wouldn't cost so much, would be something like an Apex'i S-AFC. You can do small adjustments to get a better fuel/air mixture for some more power and even some fuel economy.
For a cold air intake I think there are some on ebay that are supposed to work pretty good.
http://cgi.ebay.com/ebaymotors...wItem
Also check out these phenolic spacers, they're good for some more power as well:
http://www.nissanworks.com/Phenolic_Spacers.html
One of the best upgrades you can do is a y-pipe, those are said to give some of the biggest gains in the 3rd gen:
With high flow cat:
http://cgi.ebay.com/ebaymotors...32685
Without high flow cat:
http://cgi.ebay.com/ebaymotors...39709
Also while on the exhaust, if you want a good sounded exhaust system I recommend the Greddy SP2 cat back. They sound pretty good on the Maxima in my opinion.
You can also adjust your timing a little... I think most VE guys bump it to around 18 degrees if I remember correctly but I'll have to double check.
Since its a 5-speed I'd get an aluminum flywheel like a Fidanza, and short shifter (I recommend something higher quality like the B&M shifters, stay away from Pacesetter), and an under drive pulley.
That's all that I can think of at the moment. That should net you a very noticeable increase in power.