I have had to think about this one. I owna repair shop. When it comes to using Valvolines 3 part system, I dont suggest it to anyone with less than 75,000mi unless they are having driveability issues with no apparent ignition/mechanical issues. 75,000 is kind of like the line in the sand as to whether or not a difference can be noticed. Depends on how sensitive your butt-dyno is. Some people do notice an improvement, some dont. But it certainly isnt wasteful spending after that point. I say it like this to everyone, and have a great reputation for honesty in my community.
As far as the FI crowd goes, I dont think it would really hurt anything. We have blow-by issues already. Contaminated oil getting into the intake tract surely wouldnt be any worse than a cleaning. There shouldnt be any seals to worry about the solvents doing damage to. Any kind oftrace fluid left behind would quickly evaporatedue to engine heat. Impellers or the twin-screw "rotors" dont make literal contact so there wouldnt be a lubrication loss issue. I may do this myself just because of theoily residuethat is in the intake due to not having a catch can yet.

Just my .02

 

In our shop we would get alot of GM's with misfires. A motor vac (fuel inj. cleaning service ran thru the fuel rails usually) would work like a charm for most of them.
It should be used as a maintenance item, vs a problem solver tho.
...Strictly opinion....

 

Ditto - I put 1/2 a can of Sea Foam in the gas tank and the other 1/2 can gets sucked up into a vacuum hose connected to the intake. I do this prior to every oil change.

 

no need for that