Thanks a load for that extremely detailed answer V8Volvo. I actually bought it very very recently, I found the forum posts for the previous owner from the forum, you had tried to help him with this issue too! Though not quite as I have described it, as I've done more checking.
Boost enrichment pin is what I T'd to to detect boost, so the boost is definitely getting to there (could be an issue with the boost portion of the IP I assume though!)
Fuel system stuff is a good call, I never considered that - I have a new filter to go on, so can do that too.
It is EGR'd but will be being blanked today too
IP troubles like the cold start device worry me more, as I have no idea how to check them - I've been looking into modding the IP, and it's rather complex to say the least!
Thanks for the suggestions - one thing I meant to mention was that it's extremely clean smoke wise, so I did suspect that fuel may be related. There's essentially never a puff, which I know is odd for these - my father has one, nice and smokey. You mention the injection quantity, I'll definitely be checking that out, though I don't want to just turn it up and mask a separate issue.
I'd love to wait, but from the forum posts of the previous owner it was very overdue a timing belt a year ago! Which has not been done - so it at the very least needs done, but as you mentioned not ideal as changing multiple variables. Needs must in this case unfortunately! What I may instead do is just the timing belt, then IP belt - separately, if possible. Thanks - will let you know of any progress
