Im sure this has been discussed before in recent threads, but, What are the differences in hp gains between the two,
and what are the differences in sound?

um...i'm no expert, but i have a pop charger, and it doesn't sound quite as mean as a cai, but silversx hooked me up with a hell of a deal, it's his old one, and i saved about 150 dollars or more from getting a new cai. he said i'd get 6-8 more hp than before and i have noticed the difference. it sounds a little meaner, runs a little meaner, but cai's give you at least twice the hp if not three times.
and do you have a picture of your maxima?

i have the pr cai and i noticed IMMEDIATE gains in torque from low to higher mid-range. The sound is real deep and the thing starts making this sucking noise at 5500 rpms. It is unbelievable!!!!!

Originally posted by sexyse-r

and do you have a picture of your maxima?

Motorcities link to my Maxima
http://www.motorcities.com/contents/00HGF095900717.html

CAI makes about 5 more HP than a POP charger, sounds better too. POP charger is a rip off. Spend the extra $50-60 and get the CAI first.

Pop charger is a nice filter element, with a velocity stack, that is much more elegant than the filter on my hs intake. My pop is sitting in my basement. I should probably sell it, but I might switch intakes down the road you never know.
I wish I could have it on there with the stack and all. I heard the prcai can be set up with one. I would bet it would be good for a 1-2 hp esp up top.