Grove Street Customs optimisation

Hi, is there any way to optimise Grove Street Customs. Me including plenty of people complain about massive drops in FPS inside the dealership. It's currently hindering some of the RP that is being able to be held within the dealership itself. I'd love to hear any thoughts and suggestions to solve this issue because I am clueless as to why it happens. I think it may be due to the huge amounts of purple lighting in the interior that reflects of on the import vehicles causing FPS drops.