The only reason 158 gr. 9mm even exists is so 9mm rifles / carbines can fire a round that will still stay subsonic even though the barrel is longer.
I have a 9mm Beretta CX4 Storm suppressed - I haven't had a problem keeping the 147 gr. rounds sub-sonic, but it isn't by much. 158 gr. would be practically guaranteed subsonic.
I have the Canadian model with a slightly longer barrel, and yeah, the 147 is supersonic in it.
So you're right your cx4 must be juuuust barely subsonic with the 147.
I'm trying to find some 158, but so sad that suppressors are not legal here.