The Opel Manta, and its 1900 (Ascona) siblings, was a deceptively good car, despite not being really exceptional in any blatant way. It was the sum of its parts, as a well-engineered German car, and its single greatest asset was its handling, which was universally praised. On the other hand, its straight-line performance was always just adequate, but these Opels proved an important point: When everything else works well, and the car is a pleasure to drive, power is not the be-all. But in 1975, the Opels got Bosch L-Jetronic fuel injection, which upped power a tad, and improved driveability.
It didn’t make the Manta any much faster, but in the face of increasing emission regulations, it showed that there was an alternative to engines being strangled and enfeebled, like so many American ones at the time.