Power Seats Question

From : kit

Q: oh geez! i am lucky to see 200 miles a tank if i really took it easy like keep it under 50 the whole time. i took it to the dealer once for the bad cat and they said it just needs a tune up. i told them it was already done. now that it is making noise i am hoping they will replace it... and now that i have my motorcycle back i can just ride that while the truck is in the shop! life is good. btw the truck has 51k miles and has the original cat. so i bet that is just choking the engine. just how loud is a clogged or broken catsometimes i can drive my truck around and its fine other times you car hear something from the cat and its loud. even with the doors shut with the radio on you can hear it. but its not all the time. i can drive for days without a sound then i hear it all the way to work then gone again then back for a little bit then gone. its hard to diagnose or have the dealer replace the cat if its intermittent like that... any ideas 99 dakota sport 5.2 4x4 3.55 gears auto stock size tires. k&n fipk 10.8 mpg with mostly freeways new copper plugs cap rotor o2 sensor air cleaner belt synthetic oil trans service cleaned intake. trey i have a 99 dak sport and have had to have the cat replaced twice. they are notorious for going bad. also it is done by the dealer as part of the emissions warranty which is good up to 80000 miles. so get in there and have them swap it out. by the way my gas mileage now after my last cat swap out about 2 months ago is better then it has ever been. i am getting about 370 miles a tank. er .