That won’t help, unions are not nearly as efficient as parts nor meshparts. If you have parts, don’t even try to make them into unions, they’re not really useful anymore.
About the topic, inspect each single piece of your game, if you suspect from a specific thing like the map or the lights lagging the thing out, just take them out to another test place and if the lag is still there, well, at least it is not a virus and just a performance problem from you.