Loading Power Query to Existing Table with calculations in other columns

I am loading the results of a power query to an table. I have added additional columns to the table populated with formulas. This is working fine however when I refresh the table it is very slow to refresh. Without these additional columns, it is very quick to refresh. I turned off the calculation in Calculation Options (i.e manual) but this didn't make a difference. Any ideas how I can speed up the refresh?

Just to be clear here... which of the following are you using:

1) You are pulling in data, landing it to an Excel table, and they conditional columns are formulas in that Excel table, correct?
2) You are pulling in data, adding a conditional column in Power Query, then landing the results to an Excel table?

Ideally, you should be using option 2, not option 1. The reason is more around concerns about the formulas not extending than around speed though... If you are using Option 2, and this is where the speed is a problem, consider testing the speed with the Privacy settings turned off. You may find that makes a difference.