From what I have experienced in the past....

Loss of power at freeway speeds or during hard acceleration - Plastic in line filter usually clogging

Loss of power at low speeds, will not accelerate at all - clogged spin on filter.

No or hard start, no power at all and rough idle - Tank strainer clogged or tank vent plugged.

I would change both fuel filters at the same time and see if that helps. If not, try running the car from a separate fuel supply (jerry can under the hood with return line going back to the Jerry can). If it runs fine, that tells you the tank vent and or the tank strainer is the issue. Next would be to clear the tank vent, and lastly drain the tank and clean the strainer. When you drain the tank, if you can, drain it into filter medium placed over a bucket. The filter medium will tell you if you need to have the tank cleaned.

Good luck.

Glenn

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2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)