ISX 2250 fuel system fail

[snailexpress]

My engine wasn't running good now she is even worst.
Injector performance test can't run due to unstable fuel pressure.
Fuel system leak test fail. Pressure is down in 10seconds.
Pressure safety release valve is dry with pressure 29,000 psi
No fuel in oil detected
Cylinder cut out test is showing all 6 cylinders are equal and engine can run on one cylinder.
If connection between injector and fuel connector is not tight where fuel will leak? Inside the engine or in drain tube?
Could faulty fuel pump head leak pressure from the rail?
Any help please.