The more mods you have the more noticeable the cooler air. I have Griffin's in my '01. Both the Rad and the IC. On a cool day... 30's - 40's especially... the truck really livens up. Cool rainy days are fun too. If you are not noticing performance gains with cooler temps then you simply are not pushing enough fuel to the engine. In other words, you do not have the mods requiring the cooler air. However, your engine may not produce more noticeable power, but I can guarentee you the engine appreciates a cooler charge.