So I cleaned the EGR valve properly. It was as clean as a new one I reckon. The solenoid was free and I couldn't find anything obviously wrong except of course a build up of sooty carbon deposits as expected.
As suggested I have also checked all the turbo hoses and can find no damage at all.
Generally when driving, it's as flat as a dab until 2-3000 rpm when off it goes, often with the cloud of black smoke. Seems intermittent as occasionally it pulls through cleanly.
Seems likely that I will have to swallow the cost and replace the EGR Valve with a new one, but can someone tell me what benefits I get from it? Is it relatively straightforward to delete it, and if so, why wouldn't/shouldn't I?
From others posts it seems like these fail frequently. Will the emissions be unacceptably high come MOT time if I remove it? Does the car require specialist re-mapping if done? I was booking the car in with a top tuner to have it rolling road tuned, but don't see the point until I get it running properly first. I don't want to be paying for his time just to get it running properly.
Sorry it's a long post with several questions, I'm trying to pre-empt the more obvious responses. All views on EGR removal would be welcomed guys.