If the EGR valve itself fails you may have permanent problem of lack of power.
The EGR valve is an assembly comprising of EGR Valve (Electric solenoid) along with EGR cooler & diffuser unit.
The EGR Solenoid Valve only opens & closes to allow the exhaust gases to flow back into engine. via EGR cooler & diffuser
EGR cooler cools the exhaut gases to be sent back to engine
EGR diffuser does the mixing of exhaust gases & the inlet air & in the inlet manifold.
Generally the clogging occurs in the EGR diffuser & at the inlet manifold & not in EGR valve & cooler. since the EGR diffuser is in the inlet manifold, slight mist of oil (blow by gases) from intake mixes with the recirculated exhaust Gases (soot in this case) at the diffuser & causes sludging & blockage of inlet manifold.
if the clogging occurs severly, you may experience lack of power on sudden acceleration & black smoke.
it may require cleaning at 40,000 kms.
to avoid frequent clogging is to avoid excess filling of engine oil. and maintain the proper quantity of engine oil ( excess engine oil may cause excess blow by gases & cause frequent clogging of inlet manifold & diffuser)
if you do not experience such phenomenon - not suggested to clean EGR diffuser.
while precaution must be taken during removing & refitment of the diffuser, if improperly installed , it may cause air leak & pose more troubles.- black smoke, lack of power etc....
an expert workshop person may able to do this job efficiently.
it is suggested clean EGR diffuser & intake manifold.
avoid removal of EGR assembly as this is a very lengthy job.