I have a history on this one. Oh, yes I do.
On my Escape, I absolutely believe a clogged rear cat ruined one manifold. When you were driving this, under wide-open throttle, did the engine get to about 5,000 rpm and then refuse to upshift until you backed off the throttle – and then shift very harshly? If so, I’d say there’s a 90% chance you have a clogged main cat. Since you already replaced the manifolds – an extremely expensive job – you should replace the rear cat, or else the back-pressure (at least, this is my theory) will cause your manifolds to get very hot, and crack again.
In CA, we are mandated to use the OE parts. We have no choice – no one makes a CARB-approved cat for these cars. What year is this car? On our 2002 with 155k miles, if I was told we had to replace two manifolds and a cat, I wouldn’t do it. I’d try to sell it to someone not in CA for about $1,000. They’d fix it for $1,000, and have a good car for 50k miles. But for us in CA, this is a $2,500 job. This car is no longer worth $2,500.