Do the newer magnum style thermostats flow enough

this may sound like a dumb question but I bought an adapter to use the newer thermostats, the reason in doing so was I couldn't seem to get the original to seal. The adapter I bought is o ringed and seals perfectly. Now it seems like it doesn't matter what stat I use ( 160, 180, 190) my engine runs at 195. I know it's not hot but I would like to run a bit cooler.