Is there a Volvo mechanic near you? I notice a lot of disenchanted dealership techs will quit, hang a shingle and work at a good price. They know the PATTERN failures and how to quickly check for them. Yes, it's more than beer cans and hose clamps (KLR repairs
) but it should be reasonable. Your cheapo code reader still tells you which O2 sensor.. the numerical code does. "left bank" etc.
And, just to throw my hat in the ring... I'd SWAG the MAF has soiled the sheets. BUT..... DON'T GUESS, DIAGNOSE. Cheaper in the long run.