I just did this the other day and it seemed to work. My car wasn't having any big problems, I just had some SeaFoam and thought I'd give it a try. The car has 82k on the clock. There was one complication, the hose was rotted near the bottom and I had to replace it before I could do the procedure. But everything worked as expected with the new hose, with one exception.
When I fired up the car to burn off the SeaFoam, all the white smoke was coming out the driver side exhaust pipe, but not the other. Does this mean the ports in the exhaust chamber are plugged on one bank? I drove the car for over 30 miles after the treatment and it ran like a champ. But the following day the car threw a P0174 code. Still runs great though.
So, could the SeaFoam treatment affect the O2 sensor? Could all the SeaFoam have gone into one bank only? Which bank exhausts through the drivers side tailpipe?
I'm hoping some of the SeaFoam may have worked it's way into the carbon buildup on the other bank and another treatment will clear it out. Also, I haven't checked all my hoses for vacuum leaks, a possible cause of the P0174, but if it was a vacuum problem wouldn't I throw a P0171 also?