Original sentence: Later Golf variations included the Golf GTI (introduced in June, 1976), a Diesel-powered version (from September, 1976), a notchback saloon version called Jetta (from October, 1979), the Cabriolet (from January, 1980) and a Golf-based pickup, the VW Caddy
Edited sentence: Later Golf variations included the Golf GTI (introduced in June, 1976), a Diesel-powered version (from September, 1976), a notchback saloon version called Jetta, which wasn't as succesful, (from October, 1979), the Cabriolet,which was slower than the original hard top, (from January, 1980) and a Golf-based pickup,which was perfect for the handyman, the VW Caddy