The intention of test group no. 9 was to evaluate exhaust emissions from vehicles in Portland, Oregon which are subject to a state inspection and maintenance (I/M) program with those in Vancouver, Washington, which are not subject to I/M. Fifty 1976 and fifty 1978 model year vehicles were recruited from Vancouver and tested. Matching vehicles were then recruited from Portland and tested. The intention of test group no. 10 was to evaluate the effect of specific maintenance tasks on emissions from vehicles which have high emission levels as determined by a state I/M program. Thirty-five vehicles from the Vancouver, Washington area which failed the Oregon State Inspection Test as part of the testing required for test group no. 9 were selected for this group.