Hi there, I had a very similar problem with my 2009 D22 and it was the suction control valve (SCV). I bought an upgraded SCV from the guys at chip tuning (online). It is a simple job that you can do yourself but before you do make sure that area around the SCV is spotlessly clean as even a small amount of crap getting in there can cause an even worse problem than you have now. There is a wealth of info on there website about what a SCV does and what effect it has on the engine when it is not working properly or at all. Here is a link to there site
Front Page - Chip Tuning Australia
All the best and hope that you get to bottom of it soon.