Put a T in line with the vac line to the egr and put a vac gauge on the windshield where you can see it . See if you are getting soorce vac when you drive around a parking lot or somewhere safe. You may have no vac going to the egr...meaning no signal from ECU or bad/plugged SOV...common fault on these is the plastic vac line in front of engine cracks from heat fatique ..the line feeding the SOVs... if so , replace w/rubber line.
The reason I suspect this line is b/c you also have an AIR code[411] coupled with EGR code [400] ...and this feed line I mention is a COMMON feed for BOTH the EGR SOV and The AIR SOV..so, if both are popping a code . then it looks like neither one is getting acuating vac suppy...follow me ??????

I would also do a hand vac test at egr while engine is at idle to check flow.

PS ..if you were near these SOV when doing the other work on the car , make sure you did not swap the lines or plugs at the SOVs ... I have seen this happen to several others and the results would be the dual codes..............