the only differences in the cold air intake between 99 and 04 will be in 01 the placed the intake temp sensor into the MAF so you will need a plug to cut off the air flow since there is no sensor to put in the hole. Thats about it, if you have the sensor located behind the MAF then stick it in the hole, if you dont you best cap it off and the your good.
Cali mustangs have a smog thing in the fender on the side near the air filter and you may have to adjust its position to get the air filter to fit~ if the car is not equiped with this then your fine in that department.
__________________ 2003 Cobra Vert (Redfire) #3938 of 5082 @ 05/27/2003
472rwhp/493rwtq -Modification List - Dyno Sheet 2012 Mustang 3.7L M6 (Kona Blue) 2011 Ford Edge Sport (Red Metallic)