I was thinking on a car with over the radiator intake and a full exhaust, how would this tune differ to one on a dyno? And is there a way to improve throttle response in regards to the throttle lag?

With bolt on mods such as the ones you've suggested, there won't be a huge difference in power output between a remote custom tune and a dyno tune. We can certainly improve throttle response, nice and responsive like a MiG-29. Ok sadly not quite but you get the idea :)