I have a 3 speed circulator pump on my hot water boiler (baseboard) ....?

What speed (hi-med-low) should it be set on? I have 2 story cape-cod house, baseboard hot water. When it was installed (last year), the tech left it on low ...this year, after repeated bleeding because of water gurgling sounds in the lines when the system was turned on, the "new" tech put it on high, he also lowered the cut off temp to 160 (it was 180) because he said that even though its set at 160, the temp still rises afterwards to about 175 (I checked, he was right). He also raise the pressure in the system to about 20psi (hot), it was 15 ...does this make sense?