The 1995 to 1998 Brazilian 4.1L or 250 was supplied from the factory with 6 intake port heads and port fuel injection. It was installed in the Opel Omega (different transmission bolt pattern) and the Chevrolet Silverado truck (standard transmission bolt pattern). It also had 6" connecting rods and pistons with a shorter compression height (around 1.355")
The 1992 and earlier engines in the Chevrolet Opala used the same siamesed intake ports (3) as the US engines. They had the two-barrel intake manifolds from the factory, for either the Weber DFV 446 or the Solex H34.
A gentlemen in the US installed a port injection system on a US siamesed port engine. He removed it then installed a throttle body injection system. The throttle body system ran better with the siamesed ports due to the uneven timing flow in two of the three ports. He posts on one of the truck web sites.
http://67-72chevytrucks.com/vboard/forumdisplay.php?f=3&order=desc