i think these people are pests,additives in my opinion are expensive & not required on the modern"properly" serviced cars!
they get shot down in flames in my reception,
how can it be valve for money selling a product to a customer with no real evidence of its benefits,
watched on tv once,had an imprezza on a dyno & with additives it was down on power & less fuel efficient & all for £15,WOW
just my thoughts , keith.