[Simyacı]

Which AFR sensor should be connected to spark ems v1.1 ecu and how should it be connected?

[jonbill]

I'd advise a wideband sensor, LSU 4.9 or ADV.
You'll need a wideband controller to support it and connect to the speeduino.
Talk to the board maker about how to connect it.

[Simyacı]

Thank you very much. Where can I get the controller? Which brand do you recommend?

[jonbill]

Lots of people use controllers from 14.7,
https://www.14point7.com/pages/products
But they're in the US, so Id suggest to see what is available where you are - most will work fine.
If you're unsure of one you find locally, someone here might have experience of it.