I've been unable to set the mixture because regardless of my adjustments to the screw (I haven't done more than a total of 1/2 a turn at any one session), the duty cycle reading stays fixed at 90%. I should add that before I bought the car the OVP fuse was blown, & I had it replaced. Can I safely try to attempt resetting to a 45% mixture by major screw movement/enrichment, which I believe involves turning the screw clockwise? BTW, the tower is open on top, & I use a 3mm allen wrench for adjustments. Thanks.