well venturi is in its right place in this case, its just on top of TB as it should be, inside the element cleaner box, yes, as you cant place it under the box, same as my city 2000.
i've just came across this thread while i was searching, have a go thru this one
https://www.pakwheels.com/forums/cng-lpg/16620-strong-advice-cng-users
doing what have been done in this thread seems logical as car will breathe more easily, similarly changing venturi to one shown above with small jets pointing downwards is also a plus, starting isnt an issue in my opinion as only once in a year one need to start and efi car on cng.
i have exactly same venturi type installed at the same location in my city 2000, dont have any air blockage and didnt exactly remember how much that output port stick out into the loop of venturi but i get little over 200 on long in one tank