The 2.8 liter's a pretty sorry engine, it produces similar power to the 2.5 liter and has more parts because of the DOHC. You'd be better off doing fuel, air, and exhaust on the 2.5. But I agree, the 3.4 would be an interesting conversion. Does anyone know if any of the GM 4 cylinders bolt up to the ax-5. Because a lot of people run the Cavilier 4 cylinders in rock crawlers. The twin cam one's that is.