Glow plug is easy, just Ohm check all 4 plugs and look for one that is different than the others. If they are all alike, then suspect the contact bridge.
If it were my car, I'd probably just replace all 4 plugs if I found 1 bad one.
The EGR is also easy. The ECU uses the MAF to monitor and control EGR flow. However, somewhere in the myriad of technical bits as well as language translation, on the ALH cars "excessive EGR flow" usually means the EGR valve itself isn't flowing ENOUGH, and the actual "excessive" part is picked up through the MAF.
Now, the ALH's EGR system is brutally simple. Just a vacuum source line to a control solenoid that they call a pressure converter, then a line out to the EGR valve itself and then another vent line to the air cleaner. The feed line is tee'd in with the feeds to both the VNT solenoid as well as the anti-shudder valve solenoid. The vent line is tee'd into the VNT solenoid, too. The little diagram under the hood has all this information on it.
If the engine runs good, then your vacuum source is good... we can rule that out. So really all you have to do is determine if the solenoid is supplying vacuum to the EGR valve itself. I usually manually check the valve first, with a hand vacuum pump. Quick and easy, right on top, don't even get dirty. If it holds vacuum, then check to see if it is actually opening the valve (remove the charge air boot and look inside). If it DOESN'T hold vacuum, then you've found your problem.
If it holds vacuum, and you can manually open the valve, then put it all back together and start the engine. At idle, it should be supplying some vacuum by itself (rev the engine a couple times to make sure it wants the EGR open).
You can also do an output test with the scan tool on the EGR solenoid.
