Chevrolet Repair: Catalytic converter & Engine perf. problems, engine perf, engine hesitation

Question
Could the catalytic converter on my 1995 Chev 1/2Ton G-10 Van cause extreme engine hesitation, backfiring and stalling, if it were clogged? I recently installed a re-built "long block" (5.0 Liter-H engine) to replace an engine that was buring excessive amounts of oil. After the installation this poor performance & hestitation became apparent. I have since rechecked the cam timing, replaced spark plug wires and the fuel injectors with no improvement in the performance. A recent $300 visit to a local repair shop resulted in the mechanic advancing the timing beyond the specification. This advanced timing resulted in temporarily improved performance that seemed to degrade rapidly over time and caused the engine to run extremely poor at idle and if cold. A friend indicated that her car had a similar problem & that she simply "knocked out"/removed the converter and this solved her problem. Is there a way that I could test my converter? Any comments or advice would be very much appreciiated.   

Stumped in AZ

Answer
Yes, any restriction(s) in the exhaust will cause problems. A competent muffler shop can test the system for excessive backpressure. Also, if the engine was not prepped properly, as in cam lubed, primed and proper cam "break in" procedure followed, the cam may be going flat, which causes much as you describe. Check the exhaust first!!  Good Luck.