(And I know of one city that completely blows away this paradigm, producing Income at 20x population size. I guess I'll have to pay a visit to that city in a future post.)
whats the name of this city.
and what is your advice for anyone who wants to reduce the number of immigrants
See @bobawondua
It's an ideal mix of technology that's pretty much an end-game perfection. (Until some new game mechanic changes that approach anyway.)
As far as advice - I'm still in a situation where I need all the Immigrants I can get, my city is still pretty small. If you wanted to get rid of them, the usual techniques are to sell them in the Market or set up a second city for yourself and Transfer them.
That requires a lot of work on your part though. I think that super large cities like to reduce Popularity to reduce unemployed and the influx of Immigrants and Homeless. It's a problem I hope to have someday!