Cleaned out my intercooler, pipework & hoses in the last few days, took the elbow off at the forward end of the air intake manifold where the egr used to enter before I removed it 18 months ago, this is not a very clear photo, but my hands were covered in tarry gunk at the time
I reckon there was a mound of tarry crap about 5- 8mm high opposite the egr inlet & the manifold had a goodly layer of the same. couldn't be bothered taking it all off, so carefully cleared out the manifold with a petrol/diesel mix soaked rag wrapped around a rod & scrubbed the inlet elbow in the the same mix before replacing.
Bear in mind I remove my EGR about 18 months ago & this crud was still sat there

I wasn't getting any especially smoky tytpe symtoms, I just hated the idea of the EGR chucking all that crap back into the air inlet. So for any of you thinking you may have problems with your EGR, you probably have.
You can't polish a turd - but you can roll it in glitter.