You can use a simple vacuum gauge to chrck for restricted cats. Tie in to manifold vacuum. Your idle reading should be around 16-20 inches at sea level. You lose 1 inch of vacuum every thousand feet. Run the engine up to about 3 grand and hold. The vacuum should go in the toilet briefly and climb immediately to a value higher than idle. If it is considerably lower, chances are you have a restricted cat or retarded valve timing. When did you last replace the fuel filter? Have you done a pressure anddelivery rate check?
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