As a test, Omegatoy advised that I blank off the EGR pipe where it enters the throttle body(easy 10 minute job). I used a section cut from a coke can and evenly tightened up the two 13mm bolts to squeeze the tin over the lip and seal off the EGR pipe.
The judder has subsided significantly, not completely, but a heck of a lot better and now only happens occasionally in the 1500rpm > 2000rpm range.
I suspect next step is to remove the inlet manifold and throttle body and give them a good clean out with something like Gunk.
I may be in luck and not have an issue with the injection pump being on its last legs.
Omegatoy advised that using coke can material will only last a hundred miles or so before it burns through and that steel plate would be better, but I think(hope) I may be able to avoid this blanking by cleaning out the inlet manifold etc.
P.S
Don't let any of these tales of judders and rumbles put off any would be chippers. Earlier I had a 20 mile M4 run with cruise set at 70, with the last 5 miles being A-roads and roundabouts. As I previously mentioned, my juddering issues are now significantly reduced with further cleaning to be done...and the Average MPG display is showing 63.2 mpg.
Ask Sethsmate, he gets good MPG and he's up and down the Maesteg Alps most of the time.
OK, so let's say the display is now 10% out after chipping. That's still giving well over 56mpg at a steady 70mph.
An accurate test would be to Brim it - Drive it - Brim it ....when I can afford to fill it
