G'day buck, mate this may not help you at all?
My water pump shit itself yesterday so I replaced it today, in the process thought well may as well do the timing belt, it is due in 15000k's anyways and I didnt really want to be pulling it all apart again....BUT...while that was all off it was incrediably easy to fit up the blanking plate!
Now, I do run a chip it, I do (now) have a new timing belt, have previously done the EGR clean out, but I can say that I have noticed a difference in low down to mid range power, and although its only early days no codes or warnings. I did drill a 12mm hole in it though, thats the min you need to stop the code apparently. Food for thought....oh and heaps less (almost none) smoke out the back too!