I removed the fuel injectors and adapted a compression tester to use those ports to check compression. I believe the specs called for around 400 PSI for good compression. Mine was reading about 300 PSI with the original rings. Replaced rings and initially before attempting break in, the compression was up to about 350 PSI. I don't have much time on the new rings, so haven't rechecked the compression ratio at this point.
Someone with more expertise can probably give you better information, but this works for me.