There are two quick checks you can do to verify your suspicions:
1. Hook up a vacuumgauge temporarily, floor the pedal & observe
You should see 0 or close to 0 vacuum ( if the engine can't exhale, it can't inhale either).
2. Now it get's a little trickier. You can get a back-pressure reading ahead of the cat, if you have the appropriate gauge. Not sure what the spec's are on that engine for back-pressure, but maybe somebody else does.