Compression readings can vary widely, depending on gauge calibration, operator technique, cranking speed, engine temperature, altitude and ambient air temperature. I wouldn't take 190 as an absolute number, but more importantly, all 4 cyls read the same.

Some other posters commented on carbon deposits... they happen, but it would take about a 0.1" inch thick layer of carbon all around the combustion chamber to raise the compression ratio significantly. Go ahead and use a product like BG44 periodically, but absent any nasty running conditions, it's unlikely that major carbon deposits are occurring.
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