I'm on the same trail of thought as Neko Majin. It's debatable if Boo was that overpowered, though I definitely believe he'd gotten stronger. His steam power up seems to imply so, since that iconic aspect of his power up wasn't seen since his split into Good and Pure Evil Boo. There's also Goku stating that Boo could be incredibly strong when angry, though it's debatable how he was viewing strength comparison, since he also referred to Piccolo Daimao as incredibly strong due to the context placed on him.
My guess is Boo's currently as strong as Fat Boo's full power, so Basil wins even without the drug imo.