Hi guys! Great news... it's been a busy summer but I finally had time to work on the caddy...
I disconnected the cat and tried to run it with open exhaust to see if it would run any better - turned out that what it was!
Fortunately I live in western PA where we don't have emissions testing, so I took the cat out used a pipe to smash out the honeycomb - with a new gasket, bolts, 2 clamps and a coupler from advance, I'm back on the road for $12.00
Even better 28 - 29 mpg on the highway if I drive the speed limit on level road... but thats not easy to do in an ETC, lol
Thanks to all of you for your suggestions.