If one of the draft lines at your bar is pouring foamy, which of the following could be the cause?

The scenario describes a draft line pouring foam, and the presence of a kink in the hose from the coupler to the wall is indeed a valid cause for excessive foaming. When there is a kink in the hose, it restricts the flow of beer, causing an increase in turbulence as the beer is forced through the tight spot. This turbulence can lead to the formation of excessive carbonation in the beer, resulting in a foamy pour.

Addressing the other situations, while overcarbonation in the keg can cause foam issues, it is more directly related to the keg itself rather than the draft line mechanism. Similarly, having too much ice in the beer cooler does not typically cause foaming; it might rather lead to colder beer, which could impact the pour differently. Lastly, the wrong beer style for the tap generally refers to compatibility and may not directly influence how the beer pours from the tap unless there are other underlying issues with carbonation or serving temperature.