How can CO2 affect the flavor of my beer?

My first kegged beer has a lot less flavor (a witbier) than any other beer I've ever done. I know it could be a flaw on my part during brewing, but I just missed my target OG by .02 and it tasted fine when going into the keg. Is there something I could've done with the gas to affect the flavor?

Yes the gas in the beer can affect flavor, particulary strength. The more gas will give it a bit more sour (CO2 in water is acidic) but more importanantly as it comes out of beer in your mouth, it will carry arroma/flavor out with it. Although given that the flavor was fine going into the keg, and you would have only added air in the keg, I'm a little stumped.

As an asside, the good ice creams (like bryers) put air into their mix to help the flavor fill the mouth. I'm not sure how the air helps in ice cream since it doesn't really come out like CO2 does with beer.