1995 jeep cherokee 12k miles on rebuilt long block. just started experiencing loud popping noise from intake manifold. Disconnect electrical to #5 injector and noise goes away. disconnect #5 sparkplug wire and re connect electrical to injector no noise. plug wire re installed and electrical to injector loud popping starts back up. Took stethoscope to valve train, manifolds block and no unusual mechanical noises. Compression on #5 and #2 similar at about 65 psi. No water evident in crankcase coolant appears clear

 

It's possible that the injector is leaking. You can try swapping #5 with another one and see if the symptom stays or travels the the injector.

65PSI is waaayyy too low. Did you test it with the TB full open? What were the other cylinders?

 

65 psi is way to low..should be ballpark 120-125. Sorry didn't see Second have of above post