I'm not sure if it can be done on the Mk4, as they were designed for lower emissions than even the ABA was, but here's how I'm going to do it on my Mk3.
I already have the airpump off the car, then the two vacuum lines off (capped on the booster end, unhooked both from the SA solenoid, then capped on the valve end). I also have an airbox from an OBDI car, without the attachment for the hose from the pump.
After I VAG the car, I'm taking the tube out of the mani (the one that leads to the EGR valve) and replacing it with a short bolt (to cap it off). Next would be to remove the valve from the side of the motor, which I'll have to fabricate something to block off.
I would imagine, once the system is VAGed off, I can probably unhook the electrical connector from the solenoid on the firewall... If I do it now, I get a constant code.
I don't know how much that differs from the Mk4's, but maybe that gives some ideas. You'll have to look at the system and see how it's routed and what it's connected to. On the ABA, the valve is fed by the ex mani, connects to the side of the motor, and is activated via the solenoid, which uses vacuum pressure from the booster line. It opens, allowing the pump to draw the air through and push it into the airbox.
As it is now, if I clear the P0411 code, it comes back in a few days. However, all of my parts seem to work (which is what frustrates me) and the hoses are new and the routing triple checked. Since I don't even have emissions testing in my area, I've stopped caring about fixing it.
The main thing is whether or not those cars were available without the EGR system or not. With the ABA, I'll probably get away with it because not all of them were TLEV. I know the ABA Mk3.5 Cabrios were all TLEV, though...
Modified by ninety9gl at 4:07 PM 4-29-2007