Seafoam is 2/3 kerosene and 1/3 odorless mineral spirit, and about 5% alcohol. Of all the people ever, you are the first one i heard of that had bad experience.A marine mechanic once suggested I put seafoam in my 2-stroke outboard's tank.
It went from running like crap at idle (but fine at speed) to not running at all in a matter of minutes. I assume the seafoam dislodged junk which proceeded to plug the carb jets.
I should have ignored the snake oil advice and just dismantled the carbs for cleaning, it ran flawlessly once I had done so.
If you have heavy buildup of carbon in an engine it can remove it. I bought a 9.9 johnson 2 stroke that only ran on 1 cylinder. Thermostat was open, they ran it with choke on all the time. Got it started on 1, warmed, sprayed my DIY version of it into the intake until stalled, let it sit, 2nd cylinder fired up, after the third application it had notable power increase as the rings freed up. I would spray it into the TDI if i could.