What caused this build up

[Bowtay]

IV got a 2012 fwd transit 2.2 euro 5 it came to me with no compression timings fine whipped the head off and the inlet valves and pistons are covered in what I would say was soot looks like a good clean and reseat the valves it's good to go wondering what causes this is it a egrv stuck open as I don't want to put it all back together and get the same problem see pics

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[Cider Andy]

It's a bit crusty, intit??

My cylinder head's still on but the inlet ports and manifold look like that. Like you say, probably EGR related.

[andz327]

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