One problem related to manifold/header/muffler/tail pipe has been reported for the 1999 Volvo V70. The most recently reported issues are listed below.
Engine stutter / stall / engine speed reduced and not drivable - multiple occurrences before and after repairs over period of 5 years. Dealer repair 9/27/00 13941 miles replaced throttle body. Second instance records not readily available - believe replaced manifold. Third instance 9/16/03 36061 miles - replaced multiple components until problem went away. Fourth instance July 2005 approx 75000 miles tracs, abs, check engine light with erratic vehicle speed - had to keep throttle high rpm but diagnosis was wheel speed sensor repaired and problem went away - but starting to show same stutter on start up that predated first failure - has not failed yet, but wife refuses to drive as unsafe due to multiple failures and loss of power / speed in traffic. I believe this car is an example of the investigation in work - ref pe05041.