I want preface again that "we" perform in the shop this procedure on customers engines at least every other month? Generally speaking for the none car enthusiasts it works very well.The only way to clean the back of DI valves is to remove the intake and walnut blast them or literaly scrub the valves. The carbon build up isn't soft or gummy it is hard and baked on. Think of food and grease spills on the bottom of your oven, even with oven cleaner you have to scrub the baked on stuff. A lot of you will flame me for this but a quality dual port catch can will significantly reduce the deposits. Will it eliminate them 100%? No. Eventually the intake hs to come off and be mechanically removed. On some vehicles it is an easy proceedure, on others its very complex. Save your money on the CRC stuff and invest in a catch can, you'll be very suprised by the amount of junk it accumulates.
Catch cans:
Not all catch cans will work, work well or work at all on some DI engines. There are dozens of poorly design catch cans, universal catch cans and catch cans that are flow restrictive to the engineered designed flow rate of the PCV system on some engines, yet these catch cans sold are supported by a lot of HYP from end users. The other thing is that very few forget that on a crankcase ventilation PCV system there are two areas that you should be running catch cans. The PCV system carries an oil vapor that also travel in the breather or none positive side of the PCV system. How and why do you think that throttle bodies need servicing and cleaning on some engine that are DI? Many retailers or manufactures of catch cans don't mention the down side of catch cans and the need to have available all the specifications of catch cans offered. I really know of NONE that do that and if you call them I doubt any of them would have it either? Check it out. ha! Mainly because it is hard enough to sell something that will likely not perform as they would like consumers to think and to convince you that you need 2 catch when the world over the years has established a single catch can is really all you need. HA!
Anyone that can use a FLOW METER can do some rudimental testing to support much of my response. Also for the reports of catch cans working really well from some sources like "reviews" I noticed in most cases if you Q&A a person I often found are on high millage engine. So a properly performed compression test followed up by leak down test will often reveal that the oil contamination and the amount of vaporized oil caught in a catch can from the PCV system is mostly from an engine that is not in the best health to begin with.