Google "diy boost leak tester".
Google "air filter show down".
Searc h on the forum for cold air intake threads or CAI or best filter... and so on. The two most popular options (and the two which typically come out on top in tests) are AEM DryFlow and Apex'i. Amsoil's air filter's are supposed to rank right up there with those other two but they as well as the Apex'i command a premium over AEM. I like the AEM for price and performance.
Whatever you get don't just leave it sucking in hot air from the engine bay, you're better off just keeping the stock box and putting in a GOOD air filter.