thanks Steve.

am i right in thinking that the size of the exhaust housing directly affects power output of the turbo. i've never had a turbo car so this is my understanding - turbo runs off gases in exhaust manifold (higher revs = more gas flow) which then spins the turbine and the turbo compresses the air and creates more power. i.e. 63mm one is better than 55mm but has more lag as would take longer to reach pressure to spin turbine and boost?

is that even remotely close? lol