It is clogged!!!
Picture of my tool.
Easy! Remove O2 sensor, install "plug", connect pressure gauge. Start engine and watch pressure.
Article about:
Exhaust Backpressure

I cannot understand how clogged converter could affect fuel pressure? Unless I have 2 problems.

 

car5car, the fuel pressure for your car is a function of the intake vacuum. The fuel system normally runs about 50 psi above whatever the intake is running at. By having this constant pressure difference across the fuel injector, the computer can calculate how much fuel it is letting in since the flow rate is a function of the pressure difference.

As for how the intake vacuum is being affected, you have 3 cylinders that are not being evacuated fully. So, what happens is the cylinder is still under pressure when the exhaust valve closes. So, when the intake valve opens, you are going to get more exhaust to blow back into the intake, effectively dropping the intake vacuum and causing the fuel pressure to rise.