Hi Dean and welcome to the site. 🙂
Good to hear you have it running nicely again. (y)
The EGR valves have a habit of playing up - but you can buy a blanking plug and a 'cheater' that just plugs in to replace it from this site.
I see you've already changed the plugs but be sure that you haven't over tightened them (20Nm), especially plug No. 4 as a water gallery runs close to it and it can crack the head.
The rear suspension rose bushes, two each side, also have a habit of disintegrating (especially the lower ones) - usually get a banging/clonking when travelling over bumpy roads.
I'm sure other members will have some more pointers for you.