I'd steer clear of tuning boxes - they fool the ECU into overfueling and spoof readings to deliver more power. From experience a proper remap is what you should be looking at - an off the shelf option from someone like Revo, Racingline or APR are all proven options - or there are some decent custom tuners around too that can make a bespoke map for your car. Stay away from noddy no name garages and 'on your drive' mappers, they're peddling generic untested maps bought online
A quick look at Revo shows you should be good for 175-200bhp