Here's how it works with intakes. SRI and CAI both will flow better than stock, so that will help. The main diff between the 2 is the filter placement. You get a 1% HP gain for every 11.1 degree's you lower the intake temp. So in this example, if the underhood temp is 100 degrees (thats the air temp the SRI would ingest) and its 50 outside (thats the temp of the air the CAI sucks in from near the wheel well), that comes out to be a 4.5% HP gain, or a 5.7 HP gain with the CAI vs the SRI. Really, with the intakes, it about filter type and where the filter is placed. A K & N filter is the way to go for the 1st one. For the second part, the SRI sucks in the hot underhood air. The CAI places the filter near the wheel well, where it can suck in cold outside air. Since you get an 1% increase for every 11.1 degrees the intake temp is dropped, the colder the air outside, the more power result, in general (as the example shows). I hope this helps.