Checking for a plugged cat is easy. Use a vacuum gage. Use a hose to connect to intake somewhere and lay gage at base of windshield. Now as you drive and gently accelerate the vacuum gage drops to near zero as you approach the speed you could not get over before.

 

Well the problem turned out to be a clogged main cat. After I pulled it off, I put my leaf blower up to it and the exhaust side flowed less air than my A/C! I ran the car without the cat and ended up blowing a whole lot of pre-cat material all over the driveway. So out came the metal spike and the hammer and away went the blockage. The car runs nicely now and definitely sounds better. Thanks to all of those with suggestions, it got me to replace a few minor things. And just in time to put the top down! :rofl:

 

Nice job with trouble shooting, and a great idea with the leaf blower. :thumbs:
If the main cat was clogged im sure the pre-cats aren't to far away from failing either. You may want to consider a catless front Y pipe.

Luckily we live in a state that doesn't require emissions testing. I had my cats removed in Hawaii 4 years ago, and haven't missed em at all. :D

:cheers:

 

Thanks! And thanks for the offer of using your extra ECM. I'm guessing the front ones are empty already. Basically they blew more chunks than a senior on prom night. And each of the chunks was very black and brittle.