Unless you are buying some really cheap tint it shouldn't turn purple. The only thing that will turn tint purple is using window cleaner with amonia in it. I've had my tint on my GP since 98 and it hasn't turned purple yet. Just stay away from the amonia based window cleaner. As for the air bubbles, just take your time putting it on. Start at the center of the windows and work your way out. And don't use the rear window defrost. It heats up the addhesive and causes it not to stick anymore giving you bubbles.