Mx6 2.5i KL carburator conversation

Good day guys new to the MX6

So some tough it would be a good idea to Mount a carburetor to a 2.5i V6 KL with and old style distributor for spark im struggling to get the correct firing order diagram for the motor keeps on back firing and it's starting to kill me now

So I've tried Al diagrams that I could get on Google no luck back fires

Correct me if I'm wrong

Distributor (modified) turning clock wise from cam 123456

123546 (firing order 1 ) engine
164532(firing order 2) engine KL
162435 (firing order 3) engine

So any advice will work and help (shock for the day motor is in a BMW 😂