I haven't read or seen anything with dfi turbo cars having an issue with valve seals, but I think it could be a problem. That carbon/crude is building up on the valve's stem. That stem rides in and out of the valve seal. That seal is only going to scrap off the carbon for so long before the carbon starts to wear on the seal and cause it to leak. Once the valve stem leaks, it lets oil onto the valve and the problem will compound quickly IF THIS HAPPENS. From my friends 11k mile car, that valve seal looked to have been already been getting some contact with carbon.
WI nozzle placement leaves us with something to think about...
The closer to the combustion chamber, the better the cleaning and the better the cylinder cooling will be ( boost in octane sorta ). On the flip side. After the intercooler, but before the TIP sensor ( aka change air temp sensor ), will cool the charge temp more effectively. It also will let the pcm see the cooler charge temps and adjust timing automatically for better performance. The combustion chamber cooling will only tune its self in over time as the pcm continues to add timing in, pull after pull to until it sees knock and starts to back off. When you cool that charge temp sensor, the timing advance will be "real time live". Right then. I also like the idea of being able to SEE and LOG cooler charge temps vs just hoping and assuming everything is working since no other sensor besides the CAT sensor ( aka TIP ) can tell me its working. If I do 1,2,3,4th gear pull and my chage temp never went above 10 degrees of what it is outside ( or maybe BELOW outside temps ), then... The WI is working and doing its job. But if you put tue nozzle in the throttle body or right before the blade or tapped into the intake manifold or in a spaces between the intake/head, then the only way you'll see if the system is working, is to watch the knock corrections, lol.
Besides cleaning, I'd be in it for combustion cooling ( my pressure ratio is high, its just the nature of a turbo like this ). So I thought about duel injectors into the plenium bulge. I want max cylinder cooling and I already have a ton of control over timing events. For someone without access tuner, I'd say in the intercooler outlet pipe would be great. Me personally, that's a little hard to get to for jet/nozzle changes, so I'd goto where I could at least change the nozzles without removing the front bumper.
Seeing that with 11k miles, def got my attention.