Ford actually made a lot of dedicated CNG vehicles, Crown Vics mostly, but also F-250. My brother had a CV, now has a CNG Honda Civic. They use a similar EFI system as the gasoline ones, but not identical. They are "bank firing" rather than sequential. That means that all four on each side fire at once, just like many '90's vintage gasoline engined Fords. Since CNG burns so cleanly, the more advanced system is not necessary for emissions.

Jim