I've head some good things about Anthem Motorsports on the north end of the valley and Arizona Dyno Chip in the south east. From past experience I'd say to steer clear of www.bieberfever.com by the airport.
For Mustang clubs there's always Copperstate Mustang Club. I also recommend checking out 2005stang.com as the site has a good size contingent of Phoenix area Mustang owners.
i know everyone at AMP and just had mine dynoed.they are one of the best shops in the valley.anthem has a lot of nice cars.was going to have them dyno mine about a year ago but had a problem with the plugs,so it did;t happen.as for clubs,pima&indian school sat. nights.lots of cars.83rd ave&deer valley again sat. nights.51st ave&bell sat. late afternoons.just had flyer on car sat. early evening carl jr. 35th&bell all fords.theres probaly more as they seem to be starting up all the time.as far as copperstate mustang club goes only had one experince and was't good.