I currently have a 2019 Hyundai Tucson 2.4L GDI engine (non-turbo), 40,000 miles. Many have recommended intake valve cleaning services every 20-40k miles. BG providers offer an Fuel system/intake valve service where they use their products to clean the fuel system as well as spraying cleaner directly into the intake valve. Overall service is about $260. Are these intake valve cleaning services needed or beneficial?
Intake valve cleaning is DEFINITELY needed on GDI engines, but I highly recommend going with the walnut blasting route, not the spray cleaner route. Walnut blasting will get all the carbon junk off the intake valves WHILE vacuuming it all up. The spray cleaning will not get all the carbon off, and it may cause some carbon to break off and enter the engine, which can end up clogging the catalyst.
On a modern GDI with a proper PCV system, I'd say to do this every 60k-80k miles. To reduce the effect of carbon build-up, I highly recommend installing an oil catch-can as well, but be sure to check with your state laws first before installing one as it may fail your emissions inspection.
In fact, I installed an oil catch-can on my 2016 BMW 428i a few weeks ago, and after 400 miles it has caught all this junk. But keep in mind that my engine is tuned, and it may vary on different engines. Just imagine, before I put this on, all that junk was going inside the turbo, inside the intercooler, and inside the intake manifold 😖.