Thyme, no worries man, I have never researched what was in it, I just used it. I dont use it everytime I fill up.
My current car (82 Oldsmobile w/307) had sat for 10 years unused. I used the Seafoam Trans treatment in a flush and filter change and Seafoam in 2 oil changes. But I dont put it in and leave it. I added it and drove for a few hours, it makes the oil really dark really fast. I had a slight lifter tick, its gone. I have no proof but I am thinking it helped loosened up the varnish that was plugging the lifter so it can function correctly. I also dont know what solvents like these will do to the seals long term. I do know when you pour it in the carb it cleans the carbon build up visibley.
I have seen where people use a vacuum line to introduce it to engine and the shut it off to sit and then the impressive clouds of smoke. I have never done that. I did use a concentrated amount in a '46 Farmall Tractor, the fumes about killed me! But it ran better after the gas/Seafoam treatment.
I dont know if it will help the egr passage or not, its the only thing I can offer that I have experience with. Its like all snake oil treatments, use with skeptism.
