Haven't heard of anything specific to the Silverado. Here is a page of air filters but I am unaware of any that would drastically change engine performance.
This is a good site:
http://www.autoanything.com/air-filters/20A50341A1.aspx
Or this one:
http://www.knfilters.com/
K&N Air Filters makes several styles! A little pricy but gives you up to +26hp&23ft/lbs of torque instantly with the K&N intake and filterkit (cost about $350). They also make stock size/location filters(cost about $50) that flow more air cfm than oem stock filters! I personaly bought a hypertech power programer3 and the K&N stock size/location filter and went from average 14.9mpg to 19.7mpg! With the power programer(cost about $300) you can tune your trucks hp and ft/lbs up , change your top speed limiter up to 140 mph if your tires are speed rated for that, change shift points on your trans. , and very easy to install! go to stylinconcepts.com to check out their sale prices!