Welcome to the forum!!!
AGU are not dogs!!!
They are non-dbw (cable throttle), which most people actually prefer rather than a variable resistor (DBW).
As has been mentioned they offer more potential for large power Tuning, due to the head.
AGU's have the drawbacks that they don't have as sophisticated engine management system as the new cars, and lack a MAP sensor (for measuring boost). However, they also don't really suffer from coilpack problems. Working in the electronics industry, I now I prefer a car with less engine management than more, less to go wrong!!
I have chosen the Revo route to provide a switchable map. Revo on an AGU 1.8T is done by going to a Revo dealer. They will have to connect their laptop to the engine ECU (not a big job at all), you have to take the wiper arms off and a plastic ducting, that's all. They flash it and it's done!
You can optionally go for the SPS switch device, which allows you to s elect between the standard VW code or the Revo code. This plugs into the diagnostic connector which is found under the heater/climate control in the centre console inside the car. [very useful]
Revo may be expensive, but gives you great peace of mind if you get issues with your car, you can revert back to the stock code and see if it still occurs. All the problems I've had with my car have been nothing to do with Revo. But it means I can get onto the VW dealer to sort them out!!
It's well worth talking to Revo about the code for the AGU. Speak to Richard or Kev, both are on this forum revo_rich and revo_kev. They are very knowledge and enthusiastic!!
Here's my early rolling road output, comparing standard and Revo!
My advice would be the following:
You need to decide how much power you are looking for and what your budget is!!
The AGU comes with a K03 turbo, this turbo is only really good upto 205 BHP.
The next upgrade is a K03sport turbo, this is good for around 240 BHP.
Higher than this and an IHI turbo is the most logical, 300BHP+
Assuming you want to modify the car only slightly, here's what I would recommend!
1. Revo remap, will give you around 200BHP.
2.Get a green cotton panel filter to fit in the standard airbox. (carbino give you a lot of noise and not much else!)
3. Get a Miltek cat-back exhaust and either a sports cat or cat replacement pipe.
4. Brakes you can live with as long as you don't drive like a total maniac!!
5. Suspension, Ebaich anti-roll bars first, then if you want to improve further, coilovers.
6. Forge air intake pipe (airbox to turbo).
7...
The list is endless TBH.
Hope some of this helps!! There's loads of info out there on the forum for AGU engined cars!
BTW, I have done only 1, 2, 3 of the above so far...