Source:http://en.wikipedia.org/wiki/Fiat_X1/9
The FIAT subsidiary Abarth, in 1973, developed the Abarth X1/9 Prototipo to replace the 124 Spider Abarth as FIAT's main rally car. Ultimately, though technically inferior and slower, the parallel 131 Abarth project was chosen over the X1/9 as the main rally competition platform as the 131 model had a wider market (and therefore more marketing appeal).
The X1/9 Prototipo used an 1840 cc engine (a bored 1600 cc 124 derived unit) with a custom 16v cylinder head fed by twin 44 mm Weber IDF carburettors. Externally the cars sported flared wheel-arches, a small "duck tail" spoiler and an F1 style air intake designed to feed the carburettors cool air from above the cars roof. All the X1/9 Prototipos were raced in the traditional Abarth lime-green/yellow and orange/pink colour scheme.
The prototype nature of the X1/9 Prototipo project means that the exact number of cars produced is impossible to define. Components and entire body-shells were routinely swapped and replaced as part of the development process, but it is believed that 5 genuine cars were produced.
Pictures courtesy of michaelwardphotos.