racha
Prince
Firaxis suck so Plots given through Lua don't receive effects from Modifiers unless you reload the game. If you save and exit the plots should receive the bonuses.
Thank-you for taking the time to reply - the solution you posted works fine. Is this something that might be fixable if / when Firaxis release the dll information / code?
Meanwhile, I'm now in the market for a mod that will automatically save and reload the game every time I trigger a culture bomb.