[ShagginJet]

CAI is a CAI for a stock engine. A CAI with any sort of Cone intake is going to supply more air to the engine then the stock intake. Obviously the larger pipe intakes are good, and they need to be cold air style, not the short ram intakes. A better filer on the CAI is god too. K&N makes a couple.

AEM probably does make the best CAI, but for stock, any will do.

As for just replacing the stock filter, CAI is better cause you have a straighter less restrictive pipe and usually the cone filters are higher flow.