I installed an E.L.Prototypes Cold Air Intake in my 2001 Corolla S this past Saturday. (Like top pick with K&N filter and blue vaccum hose. Website claims a dyno-proven 5 HP/6 lb-ft increase to the wheels on a stock 00-02 Corolla) It went fairly smoothly.
I was surprised at what was involved in the stock air intake system, it was like a huge pile of plasic crap when I got it all out. :Lol: There is this fucked up resonator box thing which I didn't even know was there. It was inside the wheel well connected to the bottom of the air box. I suppose it helped cut down on noise at certain RPMs.
The fit was very tight, the fuse box had to be pushed down on top of it to get the bolt in and the battery is now about 4 centimeters to the left of where it was. The MAF fit really nicely but the new screws provided to hold it down were some wack size hex. I tried mine hex set but one was to big and the next was to small. So I figured I had an SAE set. I bought a metric set but the damm thing is in between 3 and 4mm. So now I am on the lookout for a 3.5mm hex wrench

I got them 95% of the way in using various other tools like vice grips.
My car sounds a lot different now. When you start it with the door open you can actually hear the air being sucked in, very different. The sound around town or on the highway is barely noticeable, but when you hit WOT, damm it gets very throaty. Especially at WOT from 4,000-4,500 RPMs it hits this resonance frequency and sounds like a Civic with a full exhaust
Bsides that I have noticed a ticking at idle after warm up and a slight vibration noise druing lower RPM acceleration. I think the latter MIGHT be the fliter vibrating against the engine gaurd/wheel well because it seemed a little low.
Anyway those noises don't seem serious so I'm just gonna run it and see how it goes.
Now my massive mod list includes wider tires, a strut tower bar, and a CAI. Instead of using my birthday money for a short shifter I decided to spread it out more and will probably get some rubber weather proof floor/truck matts and/or a cargo net for the trunk instead.
Well that's the news, peace guys
Chris