Makes a huge difference -- my 300TE banged and thumped something awful, and stalled all the time until I replaced the idle valve hoses. They were loose on the valve! Rock hard, too.
Clean the idle valve while you have it off -- fill with carb cleaner, shake, and dump until the carb cleaner stays clear. Wear gloves, it contains methylene chloride -- removes all the oils in you skin!
If you've had the idle mixture adjusted recently, you will need to have that re-set, too -- you will eliminate a serious air leak at idle.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!