I used to use this product with every fillup of fuel on my last car, an RX8. Typical mix at each fillup was 8oz of premix, and 1oz of FP+.
http://www.lcdinc.com/products_fuel_power.php
I can't really say if the product did its job, but what I can say is that my internals alwas looked nice and clean when viewed from a boroscope (not much carbon buildup) and my oil analysis always came back incredibly clean from blackstone labs.
I have a good amount of this stuff left over, and was wondering if anyone else ever came across it. I haven't added any to my BMW since I haven't done enough research to see how these engines fare with UCL's