Basically the EGR is a solenoid that has a vacuum tube that opens a vlave which sends a signal the the ECM.
Check vacuum line and connection to EGR for tight fit and corrosion. The main thing is to make sure the valve opens and closes with the vacuum hose attached and removed.
To clean it try using a mild cleaner that is safe on rubber such as cilicone spray and a brush anywhere neare the daiphraghm. It usually is clean in that area and a paer towlel will suffice in place of a brush.
Clean the hinged points with WD40 and a brush first. If that does nto work, get brake cleaner and use the tothbrush carfully to not get excessive amounts near the diaphragm. Keep wipping clean with paper towels and using silicone spray as it protects rubber. When you clean out any ports, spray them from the outside in. Meaning spray from the EGR towards the intake manifold or vacuum tube nipple.
Otherwise you could make clogs in the EGR worse.
After cleanering test for freaa vavlve operation with vacuum assist.
If it fails to move, it must be replaced.
Here is a diagram of its location.