I've been through this and have a procedure to test it to be sure what it is...
The EGR system is pretty simple and here are the things it COULD be:
Carbon buildup in EGR passages (VERY likely)
Bad EGR Valve
Bad EVR Solenoid
BAD PFE/DPFE Sensor
You can verify the EVR by putting a vacuum gauge in-line between the EGR and EVR. When the engine is warm and you accelerate, you should see an increase in vacuum. If so, the EVR is OK as is any systems that control when to turn it on.
If you apply vacuum to the EGR at idle, the engine should stall. Also, the output voltage on the DPFE should go up. If both of these occur, then the parts are OK and carbon buildup is the culprit.
I have a procedure to clean the egr passages, etc that works very well. A little detailed to get into here, but email & I will send info..
I've seen lots of posts about this, but a code 332 is low egr flow. The ONLY things that will throw this code are blocked passages, bad evr or egr or bad pfe/dpfe. O2 sensors WILL NOT cause this code....
It is really a simple problem to fix, once you understand the egr system and follow a logical path. I know. I worked on it for 2 weeks following threads before I sat down & thought it through....