Where is the EGR valve

For anyone who has trouble finding this like I did, if you have the V6 model of the optima there is no EGR valve on the car. However, if you have the 4 cylinder, you'll find it almost directly underneath the throttle body. It can be hard to see as the air intake hoses/MAF sensor housing obstruct the view of it depending on what angle you're looking at. There will be 2 12mm bolts you'll have to work out, you'll probably need WD-40 or similar to get them loose.

The other answer here actually shows the location of the EGR solenoid valve, good to know where it's at if you're having EGR valve related issues (error codes P0401 etc) as it can cause similar issues, but it's not where the EGR valve itself.

For reference you'll see the top (rubber) part of this image, rotated 90 degree with a vacuum line coming out of it heading towards the back wall of the engine, behind the intake manifold.