1993 Other Volvo Models volvo 440 turbo missfires at low rpm

There might be several issues at play with your Volvo. Fuel pressure and delivery, proper ignition timing and quality, adequate power and grounds that are free from issues (corrosion or loose connections) maintenance items up to date. I know this sounds generic in nature, but oftentimes it can be very difficult to deal with problems from cyberspace and can often start with checking and eliminating the basics and then moving towards the more esoteric. It may also require seeking out a local expert that has access to sophisticated diagnostic equipment that most folks cannot afford.