As far as i know the throttle body most people use is e froma titan. They also do a custom 3 inch intake and 3 inch maf housing but if you do this make sure you get a tune also other wise your ecu will go crazy and you can blow ur maf. I may be changing my thottle body but i still have many more mods b4 i even think of it. Right now i am running 240whp and 240wtq. Here is my video
http://www.youtube.com/watch?v=irlFsxQTHVI Here is also a video of me vs several other altimas on a track. The 4th gen is a 3.5 with intake and exhaust but he has a cvt transmission
http://www.youtube.com/watch?v=vBf28vUfSio . If i go for a piggy back unit i will go with the apexi most likly since ive heard many good things about it. I may just get a techno square reflash since i dont plan on spraying.