Complex sentence: By the end of 1990 they had sold over 600 kits for the various two-seat models, sales that were expected to pick up with the introduction of the Lancair IV, giving them a 30% share of the kitplane market.
Split into simpler sentences: By the end of 1990 they had sold over 600 kits for the various two-seat models. Sales increased with the introduction of the Lancair IV, giving the company a 30% share of the kitplane market.