Recently I had the opportunity to have a fuelstar catalyst installed on my ST205 Celica, as Midas in Christchurch are running a promo on the product. The Head Shareholder of Midas and their "technical expert" came and gave a presentation, and supervised the installation. Their website makes fairly outrageous claims, like "6-9% increase in power, up to 10% and more over 5000kms." Apparently the device works best on turbocharged petrol vehicles like mine. So always inquisitive, and having read the bad press and being keen for myself, I was interested to find out.
So I had a dyno done the day of the installation (it was done in the evening), at RE Sinclair (who on a side note have a very low reading dyno compared to NZEFI) and then, upon the advice of the Fuelstar people, waited 2-3 weeks for it to go through the system and see the best result. Both tests were done on BP Ultimate.
The results: well, I expected at at least a 10hp increase, that being 6%, the minimum claimed result. The actual result- a 7hp DECREASE! Hmmm. Maybe the reason they said to wait 2-3 weeks before having the second dyno was so they could get away. After contacting them and supplying the two curves they suggested that well, they didn't know what had happened. Perhaps the installation was wrong. Although if the technical head of the company can't install it properly, I don't know who can, which he conceded. Thankfully we got our money back.
Moral of the story- save your pennies! This product works entirely on the fact that the gains it claims are largely untestable!