Not sure whats causing this
 

So, I have this new (to me) 85 300SD with 196,000 miles. On the way home on the high way it felt like not going past 70. This thing will stumble and putter at anything past half throttle. I know they arent the fastest but she could only muster 45 on some slight inclines.. I can feel the cutting in,out of what must be fuel? Anyone else experience this?
This is my first diesel so would this be indicitive of clogged injectors and a tired fuel filter? I know the air filter is shot and ill be replacing that soon, but would it make it run this terribly?
Also while im at it the drivers seat is stuck with the seat tilted too far back for my tastes, it moves foreward up and down, just no tilt... all in all hopefully rather minor..

Any help would be appreciated, thanks!

Sounds like your fuel filter needs to be changed... Sometimes, especially on older diesels, you get little bits of diesel sludge and even sometimes algae that collects in the fuel tank and then gets out and clogs your filter. You may have a primary and secondary filter in your car, you should replace both, pump the air out of the fuel line (you should find a handy pump next to your fuel injectors for this purpose) and you should see a dramatic improvement. Also check the fuel lines... If they are old and "weeping" they are letting air into your fuel and need to be replaced. -As for your seat... You might try WD40, sounds like the seat is just kind of frozen and WD40 did the trick on my rear armrest...

Pretty much as previously said.
Before you change your Fuel Filters look up how to bleed the Air out of your system or you will end up with a Car that will not start.
Change both Fuel Filters. Examine tha plastic one to see if it has blackis gray green scum in it. If it has a lot of that scum you have something growing inside of your Fuel Tank and a boicide like Startron will kill that.

If it still does improve try driving with 1/2 Tank of Fuel and with your Fuel Fill Cap off. If it runs normal your Fuel Tank Vent is restricted.

If after all of the above and it still runs poorly I would suspect the Fuel Tank Screen is restricted. Swap the Fuel Return Line with the Fuel Inlet Line and make sure you have atleast 1/2 Tank of Fuel. If it runs OK like that you Fuel Tank Screen is restricted. (If you leave it like that until you have time to pull the Tank Screen out you will need to keep your pretty full as when you do the Fuel Hose swap you are drawing fuel from a higher position in the Fuel Tank; the means you can run out of fuel before you are empty.)

Less likely but you could also be having an Air Leak. If you have the Old Style shiny Aluminum bodied Hand Primer that are noted for causing air leaks when they get old. It is also Cheap just to change the 2 sections of FueL inlet hose with 5/16 inch Fuel Hose.

thanks for the help, I will be getting my filters in the mail soon!

just felt like giving an update. I spent the evening changing the cars oil and its filter. The air filter, (and cleaned out the air cleaner assembly, putting it back together with the duct seals actually in place now) I removed the little fuel filter and cut it open to reveal lots of gunk, then I removed the large spin-on filter and cut it open too. I was surprised the car would start with the amount of gunk I found in that filter. I replaced both, (filling the filter with Diesel Purge) and then cleaned out the ALDA line running to the manifold. The brittle plastic broke so I used some handy plastic vaccum line to replace it.
About 3 hours worth of work later I took it for a drive..

Well, I can safely say this car has improved 100%
It could barely make it up my hill doing 20mph. It took it at 60 like it wasnt there. So impressed. :D

Thanks everyone!

That's great! Congratulations!