Unplug the battery for a minute or two to clear the codes. 5.17v is close enough to 5v.

The EGR system not working is not going to give you the problems your experiencing. The only thing the EGR can cause is stalling at idle, and possibly some engine pinging on a hard pull. If you want to temp take it out of the picture, unplug the vacuum line to it and see what happens.(you will definitely get a code then).

If you are only getting a code 11 reading the codes with the engine off, I would look at fuel pressure and timing.