A brief history on my 97 Discovery SD V8i:
Purchased in 2012, at first sight you could tell that the truck was treated extremely poorly but bought it with plans of fixing and using it. Some of the major problems included leaking brake fluid from the gaskets below the reservoir, abs light on, did not read fuel level, speedometer not working, ran hot and eventually the temp was too high to continue driving it safely, needed new tires, rust everywhere, leaking oil many places (including the valve covers, crankshaft seal, and oil pan to name a few), windows did not work, all bushings and most all joints were shot, and definitely needed a tune up.
The Disco sat since then and recently (roughly a month ago), I was in need of a vehicle because I was involved in a collision and it was deemed a total loss, so it was time to really get the ball rolling. So I did the following things to it: new fuel pump, spark plugs, spark plug wires, fuel filter, injector filters and gaskets, valve cover gaskets, new vacuum hoses, new coolant hoses, thermostat, radiator, water pump, crankshaft seal, alternator, brake fluid reservoir gaskets, coolant reservoir cap, mostly new ball joints and bushings, and new Rotella 15W 40 oil and oil filter with new coolant.
Long story short, it no longer heats up, was running well apart from maybe consuming gas a bit more than what I expected. I've had many problems with it along the way these past couple of months while working on it, that is why I've done so many little things to it.
While driving it from work to my house which is about 3 miles, it began to not want to accelerate and felt boggy. Around half way there it did not want to accelerate at all and kept sounding like if it was choking. I managed to get it home and parked it for the night. Today in the morning, I checked the fuel pump, fuel pressure, transmission fluid, oil level, and cleaned the Maf sensor. While doing this I noticed that there wasn't any exhaust fumes coming out of the muffler and while it got hotter the engine eventually died down and stalled.
My question is, how do I go about figuring out if this is my problem and what can I do? Do I have to replace the cats or muffler if they are clogged?

 

Mileage? It sounds like the throttle position sensor, not the exhaust unless the exhaust has a severe dent to restrict flow or the cats guts are turned sideways (not likely without allot of noise first). The throttle position sensor if it fails closed will cause the ECU to initiate fuel cutoff at 1750. Might want to verify that first before trying to pull the potato out of the tail pipe.

 

160k, also after doing some analysis it reaches operating temperature quickly, and the hotter the engine is the more restricted in rpms and acceleration it seems.

 

Throwing any codes?

 

my 98 Jeep choked itself to near stall at 36k - similar to what you described - was a bad cat - which inturn cloged the muffler

 

No codes at all, it happened from one day to another basically. Glad to hear some that someone has had similar problems and a definite answer!