I have a friend that put a tornado thingy in his air cleaner to swirl the air as it enters the carb. He claims it gave him a boost. I would have to try it myself before I believe him but he says it works.
To be honest, you wont get a whole lot out of the air filter and tube. Maybe, just maybe 2-4 rwhp. They will advertise for a lot more than that though. Take my advice and get an air filter that is reusable and does not require to be oiled. The oil will get on your MAF (mass air flow sensor) and gum up the filiment, causing you to detonate like a mofo.
This is what happened to my 00 Mustang GT with a K&N filter. (before I got rid of it, the GT that is)
I had to regularly clean the MAF with electronics cleaner to keep it from giving me trouble.
I dunno, It's been my experience that 4.6L mod motors in any car take mods quite nicely. Everything from Nitrous to superchargers to cams, heads, intakes... Everything you would normally do to a classic.
For the most part the PCM's and rest of the drivetrain share alot in common with the stang and as a result there are alot of straight bolt-ons for the 4.6L cougar's...