I was always taught that its not the compression numbers but rather what it looks like across the board. If they are about for 10-15% off your usually ok.
190 across the board + 160 would be a little cause for concern since its about 15% lower than the others and pushing the limit. I would get a leak down test to see exactly where the leak is from.
valves, (intake/ex) or rings.
If its the carbon theory, I would run a little bit of seafoam or water through the car and then go for a real hard drive and see if it flushes out the carbon.