Issue with getting things clean is that the egr causes build up on the inlet tract and no additive will remove that. Best way to keep things clean , disable egr so the inlet doesn’t get clogged up, take manifold off and clean as best as possible and delete egr from the map. Getting the carbon off of the inlet ports on the head is a challenge , I’ve spent an hour with a karcher getting them off in the garden so cleaning in place is not truly possible imho, even if you think you can get into it you risk bits of carbon dropping through valve into piston which isn’t good, maybe one of these carbon cleans would
help but I’m not convinced tbh, that’s my 2 cents