Chipping

[Nigel68]

What HP gains could I get if I had my 163 CDTI SRi Insignia chipped? 

[Vauxhall Owners Club]

I think there are many different types of chips available including Tuning Boxes but the power gains are all relative to the torque increase which on a Turbo Diesel is the most important aspect of increasing power output.
I used a Tuning Box successfully on a Honda and the drivability was so much better (smoother) and the only thing that was compromised was increased clutch slippage (auto adjust type clutch).