I've had this 2000 mustang 3.8 for less than two years, it has just recently passed 200k miles and I have a 20 second hesitation on a quick take off.

 

Plugs, fuel filter, cats, fuel pump.

 

Just changed plugs, and thanks I'll get the filter asap. I hope it's not the cats.

 

If it was the cats, you would have NO accelleration. Easy way to check- get in the car, drive it around for 5-10min. Accellerate on and off the whole time. Check under the car- the cats should be glowing hot if they are that clogged.