Nedro,
The Torq Loopz are totally "invisible" when installed. They simply replace the area in the exhaust system that was occupied by the catalytic converters.
A hacksaw cuts through the header pipe very easily, (Yes they have to be cut, the catalytic converter is a welded part of the header).
Torqmaster does have clamps available that can be used to reinstall the "cats" if that becomes necessary, (SMOG testing of motorcycles for instance if that ever happens). The Loopz do give you a weight saving as the cats are rather heavy for their size, not huge, but it is there. Be sure you order the right Torq Loops for your Year GL1800, the 06-07 model is different than the 01-05 version, (The oxygen sensor was moved and is larger in the newer models).
I have the "Turn Down" model Torqmaster mufflers. It is very difficult to tell at first glance that I don't have a totally stock exhaust system with some ShowChrome turndown exhaust tips.
Closer inspection of course reveals a fully chromed muffler and a "Something sounds really good" reaction when you fire the bike up, even more so when you take it to redline. This is with optional baffles installed. There is no negative "droning" or excessive noise with this setup. I understand the Wing can be considered "Noisy" by some if you do not run the optional "extra" baffles.
As stated in the previous thread, I am happy with the change. Gas mileage has stayed relatively the same, 35-40 (real) mpg on average, (I have recalibrated my Speedometer/Odometer with a SpeedHealer to be accurate).