2007 avalanche 5.3 flex fuel 4x4 , my question is does cold air intake work

 

in theory yes, cold air is denser...the more air into the combustion chamber the more fuel you can mix into it...the more power you can generate...thats why boost is so good.
Problem:
-some cai do not separate the hot underhood air from the cold outside air at all or very well
-some cai remove the factory resonator box...the purpose of the resonator is to stop pressure wave harmonics...without it you reduce airflow throughout the entire rpm curve
-cheap filters do not meet the filtering standards of the oem filter...so you get a dust out condition...dirt into the engine=bad
-wet/oiled air filters can wreck the maf sensor hot wire

so to put it on a stock daily driver is jewellery. A performance car is the application.