If changing the Fuel Filters does not help swap the Position of the Fuel inlet Hose with the Fuel Outlet Hose. Make sure you have at least 1/2 Tank of Fuel because this bypasses the Fuel Tank Screen and draws Fuel higher up inside of the Fuel Tank.
If performance improves your Fuel Tank Screen is restricted. Only do this for the test as bacause the Fuel is being drawn higher in the Tank that means you will run out of Fuel sooner than your Gauge shows.
Also if the Linkages or the Throttle Bushing on the Fire Wall are really Sloppy the Throttle Lever on your Fuel Injection Pump will not move far enough and you will be slow.
With a cold Engine reach over and hold the Throttle Lever on the Fuel Injection Pump while someone steps on the Accelerator Pedal and watch how much Play is in the Linkages.
Things to check:
The Oil Cooler Hoses
If an Auto Trans; the Oil Cooler Hoses for that
The Drive Shaft Flex Discs
The Drive Shaft Bearing Support
The Rear CV Axle Boots (Mercedes fills them with Oil; if the Boot leaks all the lube comes out)
DIY Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum
PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles