Complex sentence: The GTI-6 was introduced as a Phase 1 model and was to last until production ended in 2002, and received Phase 2 and 3 cosmetic and electrical updates alongside the rest of the range, but with the engine and mechanical specification remaining largely unchanged.
Split into simpler sentences: The GTI-6 was introduced as a Phase 1 model and was to last until production ended in 2002. It received Phase 2 and 3 cosmetic and electrical updates alongside the rest of the range, but the engine and mechanical specification remained largely unchanged.