One problem related to gas recirculation valve (egr valve) has been reported for the 1998 Volvo V70. The most recently reported issues are listed below.
Vehicle randomly shuts off while driving. Engine shut-down with loss of power steering control. Disabled vehicle with groceries and small children inside on a 90+ degree (very hot!!)afternoon in mid-July. $322 for replacement of air flow device (meter or sensor?) to correct problem. Approx. $50, loss of perishable food.