Seafoam is a entire engine cleaner.
You get a can, put 1/3 in petrol to clean fuel injection system, 1/3 in oil to clean oil lines/channels and 1/3 you use a vacuum hose that feeds all cylinders which takes it into the pistons cleaning that out.
When you're done you leave the engine off for 15 mins, then go and fire it up, and this happens.
The amount of smoke that came out the back of my Celica when I did it was astonishing. You are advised to drive enthusiastically to get rid of the freed deposits of crap, but the first time I put my foot down the car almost stalled with a huge cloud coming out of the rear. It picked up immediately and smoked for about 15 mins of driving which is normal.
I did have a small oil burning issue on that car, seafoam stopped it completely. I guess something had gummed up in the engine somewhere allowing a little oil to get burnt and the seafoam cleaned it all off.
I need to do it on the 350 really.
You don't have to put the can in the oil either, Seafoam say you don't have to change the oil afterwards, I found you do, as did many others as it thins the oil slightly. It can clog up your spark plugs too if your engine is in a really bad state. As I say, it was fine on the celica, that had done 120,000 miles and was burning oil for at least 15,000 of those, spark plugs survived fine.
Heres a guy who has documented the process on his LS1 engine http://ls1tech.com/forums/general-maintenance-repairs/534376-how-seafoam-your-car.html