Sounds like a classic case of deteriorated precats. You will almost certainly need to replace the main cat as well since it is collecting loose precat debris.
Better check if your car is under warranty for these parts (does not sound like it).
When I had similar problem at 70,000 miles, I went with MSDS headers, high flow cat and y-pipe from BAT, and a Bosal Cat-back. I later replaced the Bosal with a stock SVT exhaust to reduce noise levels.
This has made a huge seat of the pants difference in drivability and power and cost LESS than replacing the precats and main cat with stock Ford parts (although in my case if I could have stomached dealing with the Ford service department, I could have taken advantage of the warranty).
The cost of a pair of precats when I did this was around $1500 for the parts alone.
Installing headers can be tedious but is completely doable without a lift. Mostly a matter of patience and having the right hand tools.
99 Tropic Green SVT, Tan Leather, 20K miles, "Nice Twin" (factory stock).
99 Tropic Green SVT, Tan Leather, 28K miles, "Evil Twin" (Turbo AER 3L and more in progress)
96 Red LX, Opal Grey Leather 2.5L, ATX, 22K miles
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