Typically, apart from your usual tingling/burning/irritation sensations, carbonation can activate sour receptors which can interact with the rest of your basic taste components and thereby impact overall flavor perception. Also, some off-notes, depending on their character and level, can become detectable as your carbonation level drops.

In red wine excessive CO2 is known to increase perceived bitterness of the tannins.

In carbonated cola drinks the CO2 is essential in creating the expected taste, to the extent that an unfinished drink may be disposed of as flat tasting if the CO2 has been lost. 

Dear All,

As Jerry Decker has rightly commented, lack of CO2 would create a problem of ideal taste and flavor in cola drinks. Lack of it would make it insipid. 

However there are certain fruit extract based beverages where there is hardly any need for carbonation and such beverages would taste better without carbonation. Obviousely this could be highly subjective in nature,  related to personal likes and dislikes. Also the optimum level of CO2 is important for the optimum perception of taste and flavor and this is as much true as with the temperature at which the beverage is served (as in case of relative sourness or sweetness perception).

It is quite possible that if there is any off flavour that has been developed in a flavoring component of a beverage, (say due to oxidative/hydrolytic rancidity) the perception of the same could be at a lower threshold value in presence of CO2 pressure in the carbonated beverage.

Degassing of coffee during the blooming process may be of note for your research