yes if the valve isnt opening and shutting its not working.
In fact my dealer never offered to clean my EGR Valve. He intended to replace it.
I ran a couple bottles of gumout emmission control cleaner in my gas. Then marvil mystery oil in my gas and it seemed to help.
In you case the ERG valve was cleaned already. The Mirvel mystery oil may lubericate it and free it up. It sure is worth the $3.
to try.

__________________
Steve Danville
what i did myself.
CPS
rear shocks
MAS x 3.
SparkPlugs (twice)
Fuel pump & Filter
Window switch
replaced both failed horns with Honda horns.
Cleaned ERG Tube
Oil changes
Oil consumption Fix
Brake Pads
A/C Recharge
Anti-Freeze change X 2.
Front Shocks. Monroe. $90
Mercedes Warrenty Work:
Harmonic balancer,power steering clamp. Cat converters.Drive Shaft Bearing.s
Replaced Outer Lower Tie Rods and front lower ball joints at 156,000 miles