Pat,

Here is something I found.

http://www.chevyavalanchefanclub.com...noProCold1.JPG

and the thread
http://www.chevyavalanchefanclub.com...threadid=13601

My only question is that this test was on a 03 Chevy. I have an 04 and I know that they got a HP boost from 02 but not sure if it was from 02 to 03, or 03 to 04???

If there was no change in HP from 03 to 04, then this filter and cold air set up would be a nice enhancement. But if Chevy's jump in HP was from 03 to 04 and if they did it with a similar improvement to the air intake, then there may be nothing left to improve on the air intake at this point.