what is a silicone purge valve.
There are a number of things that will Toss out and ERG code on Fords (another reason I will never own another ford as long as I live) Double check all joints around the EGR valve and the tubes that connect too it. You may have a pin hole in one of the tubes or a loose coupler. If everything checks out there. Verify the vacuum line going to the EGR is not cracked, rotted, broken, or clogged. If it is replace the line. Next you need to check and make sure the valve is opening at the correct time. If the EGR is slow to open, becomes stuck half way or is opening to quickly, these will all toss out EGR codes. Then there is the possibility that the tubes for the EGR, or the EGR it's self may be clogged as well. In which case you need to remove them and clean them out. Hope this helps in your trouble shooting. Good luck.
A purge valve is used when a system or object can sometimes be filled with unwanted substances during normal use, as a way to eliminate those substances without complete disassembly. A 'spit valve' (a kind of purge valve) is built into some musical instruments to allow getting rid of saliva which builds up inside during playing. Snorkels used for skindiving often have purge valves (some even made from silicone) to make clearing water easier. A purge valve may be used to drain occasional condensation from inside a gas line. If this is too general, please edit your question to add details.
