Complex sentence: SEAT was not involved in the World Rally Championship after the 1977 season, until 1995, when, after an 18 year gap, they returned with an Ibiza 1.8 16v driven by Erwin Weber in the Rally of Portugal, in the two-wheel drive category.
Split into simpler sentences: SEAT was not involved in the World Rally Championship after the 1977 season. But in 1995, after an 18 year gap, SEAT returned with an Ibiza 1.8 16v driven by Erwin Weber in the Rally of Portugal in the 2-wheel drive category.