did a more recent one with dyno runs
I don't think it does it justice as the test vehicle seemed very healthy pre work, it would have been nice to see similar with a car suffering restricted intake and gummed rings that was real low on power.
there was another with dpf product similar delivery method.
I do think products like this will or can work if properly administered ie over a long time.
of course removing and cleaning works also and better, but it depends what is priority to you and work being done.
I used water methanol injection(pretty random use not daily or could even monthly, not usually at all in winter months) for a few years before my manifold came off for swirl blanking, these pics are as it came off no cleaning, so I know stuff can take the carbon out.
this wouldn't even be a long spray it would be a few seconds per blast a few times when it was getting used.
of course theres areas it wont work, like here where the egr crudded up badly,w/m flowed through middle and didn't remove this build up, took a screwdriver to scrape this out.
i think everthing has pros and cons and you have to decide which way to go. some wouldn't want the hassel or inconvenience of removing and cleaning parts, and a service to drive in drive out 1hr later with minimal parts being disturbed(reduced future issues, from finger trouble on build up)
of course if your looking for performance and mpg and contemplating swirl delete egr delete etc, i wouldn't recommend wasting money on anything like this on car treatment, straight in remove and clean is way to go, youd probably end up there eventually anyway.