I will agree that the Oil Catch Can will not eliminate the carbon buildup, or need to clean. In our area (I'm in Clarence), in the cold season, my OCC catches a bunch of water, and some oil/foamy crap. I decided to collect and measure it. With the cold December we had, I get between 6-8 oz of fluid every week. I filled this 59 oz Orange Juice bottle since October 19 of this year. The dark stuff on top smells like oil, but is low viscosity (like 3 in 1 oil, a little heavier than WD-40). The necking of the bottle makes it look more dramatic than it really is, but at least 3/4 of the fluid is water.
Here is some info about my car: 08 MCSa, 83k miles, 15k per year, 20 miles driven each way to work, daily driver. Passenger PCV port is blocked, BSH OCC.
If nothing else, I don't mind not running this water through the engine.
I also see a lot of water in mine during winter and it gets very annoying to empty it every week and I don't even drive much. Contemplating to remove it as well and just do carbon buildup cleaning when time comes. Mine made it to 62k before it needed it. I removed my passenger pcv block already. My car never felt right with it, especially when I pushed the car during autocross.
Seafoam is just a stop gap measure. In the end, you end up needing the walnut shell cleaning. I did the seafoam routine for years and was amazed at how bad the valves were when I did blast the valves. Big difference in how the car runs after you do blast it - lots more air flow.
__________________
2007 MCS Laser Blue 2010, 2008 BMW Oktoberfest Autocross - Stock Mini First Place
2009 BMW Oktoberfest Autocross - Stock Mini Second Place BMW CCA Driving Instructor/Engine Mechanic/Speech Recognition Specialist