Fuel System Cleaning?

[naossoan]

Hey guys, I've got a question about fuel system cleaning.

A long time ago (years) I got a service from Mr. Lube. I can't remember how much it cost, but it was a fuel system cleaning they did. They said I should do it every year.

They hooked up my exhaust pipe to a hose leading into and out the top of their building to properly exhaust the toxic fumes. Then, they had this what looked to be an aerosol can of whatever cleaning product I don't remember the name of, and looked like he had hooked it up right into my fuel injectors or something. He plugged it right into the engine somewhere.

Then he had me start it up, idle for a bit, got me to hold it around 1500 or 2000 RPM for a few minutes, can't remember at what RPM it was a exactly, then back down, then maybe up higher around 3000 RPM for a short time.

Meanwhile there was this horrible black smoke coming out of the top of the shop, which he told me was all the shit coming out of my fuel injectors and other such things.

At the time I knew nothing about cars so I figured this was legit. Is it all a bunch of BS or what? Does it just do the same thing as the $4 bottle of Fuel Injector Cleaner bought at Canadian Tire (that I just used btw) does?