First question I have - what is the purpose of CRC turbo cleaner?
As for the oil - at 20k miles it is a bit too early for oil leaks; however, not knowing the history it is hard to say what happened to the car before you.
Let's look on it from a different perspective.
If you (previous owner) used wrong oil, say cheap 5W-20 (very common one, and used in NA Forte) due to lack of knowledge of the service dept, I could easily see it being vaporized and being pushed back to breather, and drip into the filter filling the box.
Especially in desert in Texas.
I use 5W-30 in Michigan and I DO see that. Oil is quite clean, though. It is expected, maybe not normal per se.
Another thing that may be happening, is oil in turbo. It is sucked into the intake through breather or the shaft has small internal leak and travels to hot pipe and through intercooler. Most of the time ends up on the engine, but sometimes it will be pushed through BOV to the intake, and drip, drip, drip...
If you want to check it - clean the box. Drive for a few days and observe.
Also, disconnect all pipes (hot, cold, at the turbo - top, intercooler return) and check for oil residue.
That will give you an idea where the oil is coming from.
I personally would let them work on my car. I would really suspect being wrong from the factory, as it is a very stretched accusation now for the 2nd owner. 15k miles is a lot of time to mess up any car.