Keep in mind that the direct injection was only availavle for the 2004 axiom,any older axiom doesn't come with the direct injection.

The 2004 Axiom comes with a 250hp stock engine while the 2002-03 axiom comes with a 235hp

The increased in the HP for the 2002-03 axiom was its electronic throotle system,better intake plemum and better cylinder heads + few other improvemets.

The 2004 axiom comes with all the above mentioned improvements + the direct injection feature.

According to iam ironman you can swap an axiom long block engine that comes with 'X' as the 8th digit on the VIN