Dont know about the 1600, but i fitted one to my 1300 (new from Weber for £270) and it has made a bit of a difference. mpg was around 30, now around 40-45. Couldnt say for sure it was the carb though, as i also adjusted the timing.
Thing with these is they are easy to tune (tuned the mixture myself, got a garage to check it - it was free for me but it is only a few mins check and wouldnt cost much from a small local garage with a CO meter) and there are few things to go wrong.
Choke can be found here, along with a brand new weber if you have the desire:
http://www.webcon.co.uk/shop/shopexd.asp?id=9019http://www.webcon.co.uk/shop/shopexd.asp?id=959Weber were very helpful whenever i ran into problems (first was old instructions for a the DMTR carb, second was regarding the fact that DMTL doesnt have a return, overcome with a T-Piece)
First though - read the guide by Rubyjohnny... ver yhelpful for the 2E3 carbs