The higher temperature of the intake valve of a GDI engine, creates "lava rock"
Quoting GDI, he says.... ( in 2016) same Colorado fans forum mentioned above ....
"Seafoam, BG, CRC, X66P, etc. are all basically the same make up. Ford has release bulletins that is will void warranty on any ford GDI engines, but have not seen GM issue the same yet.
These are safe
or port injection engines
as the coking deposits are the "soft carbon"
and very little to loosen and expel.
GDI engines the valves run far hotter
with no fuel touching them any longer to cool and clean them, so when used, these absorb into the deposits causing them to swell and expand and break loose a portion and most is then expelled out the exhaust
where it makes contact with the catalytic converters and clog's and/or causes damage from the cooling shock of this solvent hitting the catalyst honey comb material when it is up to temp.
The real damage though is from the smaller particles forced down between the pistons and cylinder walls as it can be as hard and abrasive as sand. That is never good as the scratches/scouring left allows even greater blow-by and oil consumption.
We also see a high incidence of rod bearings failing shortly afterwards if oil and filter are not immediately changed to remove the solvent and particulate matter forced into the crankcase.
Now on port injection engines, these have been and can be used safely,
but they do not have intake valve coking issues like GDI engines."