I think every car is different and every car has it's own demons... well mine was this bloody rough engine idle or engine surging as Subaru Australia called it. This may not be the fix for everyone's issue, but it did help mine.
After alot of googling, reading and searching I paid Paul Fisher @ Pulse Racing (Menai) a visit to see if he could look into my issue. Along with something else.. but that's another story
Previously I had been to Denlo Subaru 3 times to see if they could resolve this issue, but to no avail. Loose intercooler pipes, reflash the ECU, engine clean etc.. etc.. still couldn't fix the problem. I also clean the AFM with contact cleaner as suggested. These fixes did help, but the issue came back, that is not say it doesn't work at all, it just didn't work completely on my car.
So I went to see Paul and he hooked up his little computer and saw some readings... advised that he thinks the front O2 Sensor is probably playing up.
I replied "but Subaru advised that sensor is fine, no error codes when they checked"
Paul showed me the actual reading on his computer and it was flickering up and down during idle... "this was not normal, it should be steady until you give it abit of gas. Sometimes it may just be that it is not working 100% but still working and that's why Subaru didn't pick up on it..." So yeah I checked my car and for a full diagnostics....
Yesterday picked the car up, Paul advised it is now full fixed, guaranteed this problem will not come back. Front 02 Sensor was replaced with a new one.
All I can say SO FAR is that my GT is now purring the way it should be, but I'll report back in a weeks time just to make sure
What a relief SO FAR to say the least.....