One of the fast ford mags did accuracy tests on boost gauges a little while back and gave some very suprising results. They tested shit loads including the auto gauge that I bought from halfords which I thought was cheap cack but turned out to be one of the most accurate! I remember the Tim gauges turned out to be one of the most innacurate. Wish I could remember what mag it was as I threw it away after reading ( mate gave me loads) it was either performance ford or fast ford. Hope that helps