I had the pleasure of using this guide a few weeks ago on my Agu 1.8t
I also cleaned my I.A.T sensor (intake air sensor) using carb cleaner and a tooth brush (my mrs doesn't know it was hers)
Before cleaning the T.B, the car was idling very rough, struggled to start without giving the pedal some gas and would constantly stall at junctions and traffic lights. I was lucky if I got 18mpg around town (normal driving).
After unbolting the throttle body it was clear it hadn't been cleaned for some time. After a good scrub and blast of cleaner it looked as good as new. The I.A.T sensor was just as bad, I used a toothbrush and carb cleaner to clean the wire of the sensor, it was caked in black carbon and took some careful cleaning.
When all was back in place I turned the car over and it started first time no problems idle was high at 1800rpm for about 30secs then settled at 900/1000rpm.
It now runs much better, throttle response is smoother, no more kangaroo jumping and stalling and I easilly get over 30mpg around town (normal driving).
I recommend cleaning the I.A.T sensor at the same time it's only one allen bolt and a wiring plug to remove and it's out.
Worth trying before chucking big money at expensive replacement parts
