So if I put one of these on my X, what kind of improvemnts am I going to see?? Will it make it impossible to smog in Ca? Will it improve my gas Mileage?

Thanks
Phil

The system is 50 state legal so you should have no problems smoging in Cali.
I just did the stock airbox mod and added the Nismo 3 piece exhaust system to my 04 SE S/C.
I got my Exhaust from here : http://cgi.ebay.com/ebaymotors/XTERRA-CAT-BACK-EXHAUST-SYSTEM-STAINLESS-STEEL-CATBACK_W0QQcmdZViewItemQQ_trksidZp1638Q2em118Q2el 1247QQcategoryZ33630QQihZ014QQitemZ330193756469QQr dZ1QQsspagenameZWD1V
I did the best offer option and offered 240 for the system and 60 for shipping and they accepts so turned out ot be 300 shipped to my door and i recieved it in 2 days. They also sent me front and rear carpt for free.
the sound is a little bit louder not ricerish.
i ran 2 tanks of fuel through it since and gained 25 miles the first tank and 18 the second. I am gaining about 1-1.5 more miles a gallon.
I instaled the system myslef would go smoother if you had a buddy help.

got the same one. Having problems with the piping starting to rust. As are others who've ordered from the same guy on Ebay. Kinda makes you wonder, he's sold like 100 of these the past year at a fraction of the cost...

At that price it will pay for itself within a year or so... .I guess Im gonna pull the trigger....

Phil

I just got mine in the mail, I am trying to price quote some federal down tubes to try to squeeze even more power out of it..