Finally got a boost guage. Nothing special, 2-1/8 mechanical. I have it tied into the port that is on side of sensor that sends boost signal to Roush boost-a-pump. Getting into boost, guage needles bangs (flutters) like crazy. I assume it is reading the boost spikes from the blower rotors? Is there a better source and/or something to put in the vac line so it "normalizes" that vac/boost signal?