the box should be ok with that power i eventually broke a cts stage two with my 1.9cvh plus nitrous, i changed to a stage two plus but i have the box checked every year by cts and there is always parts which need changing.. the bc box internals just fall apart with huge torque but at lease the cts stage two plus is a big improvement from standard..

wing can you describe the noise and are you sure its the box?

sean