Do cold air intakes work?

Just wondering if they really do help with performance, if ever so slightly. Wouldn't you want the hose to be as short as possible? Will I notice a difference if I use only the cone filter with the stock hosing? Just in general, not targeted at a specific car (or at least among 4 bangers).

Will something like this be worth buying?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=38634&item=7931412904&rd=1&tc=photo

In a word, no. Sometimes they claim 15 hp, but that's with other mods usually. In general, any stock intake system will suffice, and sometimes the cold-air intake is worse. On older BMWs there is no benefit (other than the howling sound) from the cone filters and cold air ducting.

If your engine truly needs more air, it helps by a few HP, but otherwise, no.

well i wouldnt say it that way. a good cold air intake that is properly designed will. maybe 2-5hp to the wheels from a small 2-2.5l engine. a cooler charge and less restrictive air filter will always help an engine. if your a person who wants to see results get a boost/vaccume guage and put it on your NA stock intake with stock filter. drive around, do a few hard pulls. like say if you where passing. going 60mph, down shift to 3rd and put it to the floor. if there is a vaccum in your intake then your engine is stucking for dear life and there is room for improvement. next (if your the experemental type guy) get a K&N replacement filter for your stock airbox. re-try your driving test. if there is still a slight vaccum then there is room for filter/intake improvement. if not then then the only thing that will help the engine in its current state of performance is a cooler charge (note, there will always bee a small vaccume in the intake if its not FI or a properly designed RAM air intake, fluid pressure drops when it flows, thats a fact of life). lets say the intake tempature of your engine after it has warmed up is 100 F. if your cold air intake will allow an 80 F intake charge a noticable power increase will be seen. some stock intake air boxes already pull fro mthe fender well (my mothers nissan frontier does and her cavilier did also). if that is the case then a CAI system will show no improvement over the stock intake system if the stock intake was flowing well enough.