2.0 tuning guide.
These are scans from the August 2007 Eurotuner.
They talk about upgrades for the 2.0. Its hard to get back issues, they do not
sell them online.
Yes, the AEG (MKIV 2.0) is almost the same as the ABA. (MKII 2.0) With the exception of the ECU and a few other parts. So most of these mods fit (or have a MKIII version).
In a nutshell if you have a MKIII 2.0 you'll want the following.
A K&N panel filter, with a gutted air box. ($50)
A Chip (TT, GIAC, Autotech) ($100)
And an Exhaust of 2.25" with a high-flow cat. ($500/700)
Then a cam. (TT's 270 is a nice choice). ($250 w/parts)
But if you want further reading, here you go. Its not perfect, but its not awful either.