You need to check the compression, it’s the only way to know for sure.

If you have a 61x series engine here are the compression specs:

The service manual indicates an acceptable range of 24 to 30 bar or 348 to 435 psi. Minimum pressure is 15 bar (218 psi) and the allowable difference between cylinders is 3 bar or 43.5 psi.

If the compression is good then you obviously have a leak somewhere.