Although some of you are quite correctly stating what the piston engine manufacturers recommend, one must bear in mind that they wrote that advice for USA conditions.
In South Africa ( say Johannesburg altitude 5500 feet AMSL) most un-turbocharged/supercharged piston engines produce better power with a correct slight leaning procedure applied - before take-off.
You mean you have different air in South Africa? Perhaps a different atmosphere, with a different combination of 79% nitrogen and 21% oxygen?
Think about what you wrote, and perhaps correct it. It did bring a smile, though.