true does depend on the cars, it works marginally on some cars, and is expensive. I'm leaning towards adding toluene by it self that costs nothing compared to the ready to buy "special" mixtures off the shelf from repco and supercheap autos, and you can play around with the levels and a piggy back ecu to find the sweet spot. The sweet spot in my jap car is 2 and a half bottles of additive (can't remeber which brand but @ about $20 -$25 each it isn't worth it) or under 50cents of toluene that does the same job.

But that's in the skyline, only car I have that can read ping/detonation while it's driving

Edit: just googled, looks like i'm not the only one who thinks most of the pre packaged octane boosters don't work, on my car it doesn't make a difference, the others don't need it. But of all people you would know a 550 more than most others. In my own insignificant experience toluene is the way to go.

http://www.skylinesaustralia.com/for...html&st=20