I am wondering if anyone else has used the turbo 108 octane booster in their Grand Prix GTP supercharged? The car calls for premium unleaded fuel, but I hate paying the extra 20 cents or so for the premium. I know I should use premium fuel all the time to prevent knocking and what not. If I fill up with 87 octane and then use the turbo 108 octane booster, that should produce the same effect as using 93 premium octane fuel, right? Is using the turbo 108 octane booster good for the engine performance? Or is this not recommended for the 3800 series 2 supercharged engine? Thanks!