Cummins ISL compression percent

[Kiko]

Hello All. I am wondering if anyone on here knows what the compression should be on a ISL engine. Cummins does not like to use compression psi but wants to use blowby tests. This is all fine when testing but does not tell me what cylinder it might be. I am getting blowby excessive codes and engine was taken to cummins to test. They reported that the blowby was to high. I want to check compression at the cylinders first before condemming the engine for a rebuild. Also would like to eliminate everything else first like compressor and turbo. We inspected both all ready and don't see a problem just jumping out. Engine appears to run fine and operator said no loss on performance. I have an old injector that we converted into a compression tester but can't find actual specs. The only thing I can go off is that a diesel engine should be 300 plus and relatively close on cylinder to cylinder. Thanks in advance.