Sports Compact Car is the best tuners magazine out there, that and Super Street, with SCC more technical and Super Street more show and lifestyle. Import Tuner is straight lifestyle and show, with a smattering of technical stuff. Turbo is alot about the dragstrips and some technical stuff, but I dont think its worth when you can get SCC for the same price and three times the content.
For regular cars, I like Road and Track, but the editors of Automobile have the same opinions as I do. Motor Trend is pretty bad. If you want some good stuff, get Evo or TopGear, the British magazines.
I would say Grassroots Motorsports and i personally like Road & Track and Motor Trend. I know they aren't all import stuff...but what can i say...i'm an American Muscle car fanatic stuck in an import car...for now.