I would check the fuel pumps. Also the fuel distributor is probably all gummed up. Does it sputter like it wants to accelerate or does it feel like it is running like it should if it only had like 50 horsepower? When the fuel pumps were failing on my 420sel it would sputter real bad because I was starving for fuel.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual