I got stopped on a test drive in a Celica a few years back. The cops came on all aggressive and accdued me of driving through a red light. I had been speeding but no way that I had done that. Anyway, I was very polite with them and their attitude changed and they eventually waved me away.
I honestly believe that they stopped us because we were two young blokes, one in a baseball cap, one Asian, driving round the Liverpool suburbs in a nice car and they wanted an excuse to check us out.