How to do the reset? By simply starving the car’s ECU of electricity.
How to Zero out Your Volvo’s Computer and Make it Re-Learn your Driving Style
Since all 1990s and 2000s Volvos’ ECU’s have volatile memory and rely on a constant supply of 12 volts DC from the car, disconnecting the battery will do it. Follow the link below for more on this procedure.
“When my MAF sensor went bad, I changed the sensor and the car ran afterwards – but it was reaaaallllyyyy slow until the turbo picked up, and I noticed black smoke out the back. Once I reset the computer, it instantly had its pep back.”