FWIW, there are two different ways of doing Seafoam treatment. One is through the tank, like Techron. For a GDI+MPI engine like the 2.5T, this works,
with a caveat... How much fuel is sprayed through MPI depends on how the car is driven. My edumacated guess is that for hwy cruising at steady speed, most of the fuel is injected through GDI. This maximizes efficiency and, if engine load is below a certain threshold, ECU can go into stratified-charge mode to achieve even lower fuel consumption. IMO, if you do the thru-tank fuel treatment on the 2.5T and then cruise on the fwy for the entire tankful, it is almost as pointless as doing the same on a 2.0T or
3.3T.
I'm also guessing MPI is used most under varying engine load conditions, like driving in stop and go traffic, or when max fuel delivery is required. I'll be doing my Techron treatment based on these premises.