NC EGR Valve - sourcing a replacement

Hi, just did a search on PO304 fault code and it comes up cylinder 4, misfire, have I gone wrong somewhere?

You don’t want to buy a valve if that’s not the problem.

Have you got a misfire, all be it intermittent, or a slightly rough idle?

 

http://p0304.enginetroublecode.com/mazda-mx5