Great, thanks for the info Baz.
Come to think of it, I do remember seeing some boost gauges inside - so that must be it! It was looking very nice, all the nice cars made me feel jealous about how standard mine is. It just sounds silent!
The cars were looking very nice parked up next to each other, the monster really is a beast. Unfortunately, I cheacked back a few times throughout the day and never ran into the elusive owners, would have loved to have had a chat though.