as indicated at 79 of fig1 and it may be in pneumatic communication with the vacuum reservoir 91 of vacuum operated wastegate actuator 72 as shown in fig1 the fourth plot from the top of fig2 represents wastegate reservoir vacuum versus time the x axis represents time and time increases from the left to right side of the plot the y axis represents wastegate reservoir vacuum and vacuum increases in the direction of the y axis arrow the vacuum level at the x axis is atmospheric pressure the wastegate vacuum reservoir may be arranged as indicated at 91 of fig1 and it may hold vacuum to operate vacuum operated wastegate actuator 72 as shown in fig1 horizontal marker line 206 represents a predetermined vacuum level in the wastegate actuator reservoir where engine air intake filter degradation may be present a vacuum level that is greater than the level of horizontal line 206 indicates a condition of engine air inlet filter degradation a vacuum level that is less than the level of horizontal line 206 indicates a condition where engine air inlet filter degradation is not indicated the fifth plot from the top of fig2 represents an engine air intake system diagnostic mode flag versus time the x axis represents time and time increases from the left to the right side of the plot the y axis represents engine air intake system diagnostic mode a value of zero indicates no engine air intake system diagnostic system evaluation is presently being performed a value of one indicates that an engine air intake system diagnostic system evaluation.