I'm skeptical. They don't show any actual dyno measurements. Also,
if there is 20+ hp in the ECU (and 20 to 40% torque) you can bet Volvo
would have pulled it out to use. Volvo went with a 5 speed automatic
in 99 to improve acceleration and a software change would be cheap in comparison (they also went to variable valve timing; again, not a cheap
way to get power indicating the cheap power tricks for the engine have
been done by Volvo).

The site also says they use 98 RON fuel (that comes to 94 PON
octane; PON is what you see on U.S. pumps). Do they have 94 octane
fuel available where you live?

U.S. $800 for an ECU mod like this seems a bit too much, too. Now,
it is actually a good deal if they deliver. But I'd want to see
dyno charts using pump gas first with a 100% (no 15% stocking fee)
gurantee.

The stock filter flows enough air for the turbo so I don't think
that is a weak spot.

Exhaust change might help a bit. But they can also reduce torque
and improve horsepower (or vice versa) depending on how they are tuned.