When a cat plugs, you'll usually notice a reduction in top end power, followed closely by the engine not being able to rev past a certain RPM. It is POSSIBLE, but I'm going to say that is not your problem, given that you still have top end and have just lost mid range power. Check your fuel pressure KOEO, then KOER at idle, then tape the gauge to the windshield and drive it on an empty stretch of road or large, deserted parking lot and monitor you pressure at cruise, WOT and light acceleration. See if it falls off when you lose power.