[Quacker]

The only thing tuning boxes really do is raise the fuel rail pressure by altering the reading of the pressure sensor to the ECU.
There are some expansive ones, like the Steinbauer premium range that connect to individual injectors, but you are just as likely to throw fault codes in my experience. If you have a local Steinbauer area rep who will stand by the product, great, otherwise I wouldn't risk my money on any plug-in device.

Remaps are a different story. I had tuning boxes fitted to Range Rover and a BMW X5 and it did hardly anything to them. However I had a remap done on the Q7 and it really did work and was most impressive. Today's cars have ECU's that are locked down and require the ECU to be removed and some chips changed inside to allow a remap, so it's not as simple as it once was.

Honestly though, think about it. How much more power and torque do you think an emissionised 2.0litre diesel four cylinder can take before you risk major faults and big repair bills down the line? This Volvo turns out as much power and torque in standard form as my Q7 three litre six cylinder did after a remap.
The fuel rail [common rail] is pumped up to a constant 2500bar [36,500psi] on the standard engines. A tuning box might well increase that by over 10% to 2750bar [40,000psi]. Do you really think that is desirable and conducive to the CR pump and injector longevity?