Just looked it up, this is what they emailed me:

The upgrade is guaranteed by us undetectable by BMW service and diagnostic equipment and there will be NO smoke. We take the car to around 340 BHP and 535 lb/ft of torque. Cost £795+vat and the work can be done at your location.

535 lb/ft is 725nm. This is significantly better than the Superchip way I'd say.