K&N FIPK: Is it worth it?

I bought the MAC CAI for mine that curves into the fenderwell and we get alot of rain down here in texas. When I put it on I felt a increase in acceleration....I'd say they probably add like 5hp and they make your car sound better also because you can hear it sucking up air and it sounds way better than stock. When I put mine on it made a whining noise like a supercharger would and i felt special and I pretend I have one on my car and keep dreaming that I really do! lol.
 
TrevX said:
I bought the MAC CAI for mine that curves into the fenderwell and we get alot of rain down here in texas. When I put it on I felt a increase in acceleration....I'd say they probably add like 5hp and they make your car sound better also because you can hear it sucking up air and it sounds way better than stock. When I put mine on it made a whining noise like a supercharger would and i felt special and I pretend I have one on my car and keep dreaming that I really do! lol.
CAI 1 or 2 hp!
 
Cut/paste from my CarDomain thing:

I’ve seen the air temperature argument so many times and thought to myself, this was something I could easily validate. I went to the hardware store and looked for indoor/outdoor thermometers. I found this digital thermometer with an outdoor sensor on a 10’ wire for $10. Perfect! I bought two so I could take temperature readings in the engine bay and in the fender at the same time. I hurried home and opened up the hood. I attached one sensor along the front brace, just behind the passenger side headlight. The sensor was about two inches in front of the K&N filter in the engine bay. I attached the second sensor to some cable inside the fender. It was about 4 inches into the cavity for the air silencer. I ran both wires into the car and attached the two thermometers to an old CD. I rechecked all my connections and I was ready to start my data collection. The geek inside me was happy and I’m sure I got a few weird looks from the neighbors. Time to drive around.

The data tells me that once I am moving above 15 mph, the temperature difference averages around 3.5 degrees. With the a/c running, the engine bay was around 4-5 degrees warmer than the fender area. At speeds less than 15 mph, the difference goes above 10 degrees. The engine bay is definitely hotter but only by a few degrees when the car is moving.

Does the air temperature matter? I can’t answer that. I’ve seen some claims on the Internet about losing 1 hp per 10 degrees increase in air temperature. If we assume that is true, then having the filter in the fender gives you 1/4 to 1/2 hp over the guy with the filter in the engine bay.

Do I miss that fraction of a horse because I got the K&N FIPK? No. If we assume the 1 hp per 10 degrees is accurate, then my car will produce 2-3 hp more in the early morning than my drive home at 5:30 pm only because of the weather. The 1/4 to 1/2 hp is negligible.

Does the extra half hp result in better mileage or performance? In a laboratory or on paper, Yes. But in the real world, a slight incline in the road, or a light wind, or having a passenger, or a little traffic will have so much more impact on mileage and performance that the 1/4 to 1/2 hp is again neglible.

My recommendation is to choose a CAI that has the larger filter for more surface area, and one that has the shortest path to the throttle body.