Congrats on the install. They are pretty neat devices. For my gauge install, I used a VDO 0-15psi gauge (I like to see the needle sweep the entire range) and used industrial velcro to attach it to the instrument cluster right above the front left speaker. The wires for the gauge illumination and the tubing that sends the boost all were routed up from under the speaker grille. I thought it was easiest to see placed here, I didn't want to get rid of my ash tray, and I thought that putting it near my right knee would be inconvenient.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside