I get 85-90 KIAS out of my 150 but tend to run it at 2400 rpm or a little above most of the time. Rarely would I use much less than this, so I'm with the others, try pushing it a bit more - if you're in doubt it may be worth getting the RPM gauge checked out with one of those handheld digital strobe meters, some gauges can be out by 100 rpm or more without you being particularly aware of it. So while 2200 is quite low (for a 150) already you could find it's actually running at 2100 or even less. I wonder what it indicates when you do a static check? If you look it up for the particular prop you have etc you should be able to get a reasonably accurate idea of your expected static RPM and see if it differs much from that.
FWIW the 152 I fly doesn't perhaps appear to work quite as hard as the 150 but in practice there's not an enormous difference in route times between them.