This is my second GDI GM vehicle. The first was an 08 Caddy CTS withe the 3.6 V6. At about 40k miles, I noticed a puddle of oil in the intake tube. I pulled it off and cleaned it. While it was off, I notice the TB was oily. Cleaned that as well. Looked into the manifold. It was full of oil. Pulled the upper intake and cleaned that. While it was off, I could see the intake valves, they were totally gummed up. Spent another 2 hours cleaning that up. I ordered a catch can the next day. Everything stayed clean after that, at least until I traded it at 111k for this truck. I used to get about 3-4 ounces of fluid out of the catch can every 4-5k miles. The fluid was a combination of oil and water vapors so it looked like chocolate milk.
Therefore, I am sold on the need for a catch can on all GDI engines. The new Fords went to a combination of port and direct inject, my guess is to combat this issue.
My old was was an RX, but I can't seem to find them anymore.