If you have over carbonated your beer, it's going to be over carbonated for quite a while, even if you turn the CO2 down. That aside, since you have a tower, you might be experiencing "first pour foam," which happens because the faucet/shank tend to be warmer (at first) than the beer. Pouring a second pint immediately after the first can help diagnose that.
If you've eliminated a warm faucet/shank as the problem, and if you know that the beer had not been over carbonated, there are several factors that contribute to balance (or unbalance) of a draft system. Here is a step by step method to balance the system:
- Determine the average temperature inside the fridge.
- Decide how many volumes of CO2 you want
- Using a keg carbonation chart, find the PSI needed to maintain the CO2 level you chose, given the temperature
- Given the PSI from the previous step, determine the length of beer line (given the Inner Diameter of the beer line you have) that you need to balance the system, so that the beer exits the faucet fast enough for a reasonably fast pour, without excessive foaming. There are calculators that can help with this last step.