Hello,
On my Australian compliance 1995 disco auto tdi, there is no Catalytic converter and no EGR valve. I do have the 2 mufflers though.
I carried out the fuel mods suggested, and today took it on a 300km very torturous trip with many valleys and hills mostly with 100km/hr speed limits including up a mountain. I found that the mods have make a difference, the feel of the vehicle is slightly different, seems more torque at low revs but its very subjective. Trying to do 100km/hr up a steep mountain and keep up with the rest of the traffic is still just as impossible in top gear as ever, and I still have to drop to 3rd and be happy with 80km/hr at about 3000 rpm.
When my exhaust pipe SS extender arrives from the US, I will chop off the end muffler leaving the middle still in place but thats about as far as I want to risk it. Noise laws are quite strict here (same as California).