Not sure which year got the upgraded fuel injectors. But I think it was 01. Some of the 01s have yellow top 19 pounders while the later 01 and newer got the pink top 21 pounders.
And along with the water pump pulley that was mentioned, the alternator pulley might be slightly different. Along with the alternator brace. I think they went from a 3 bolt alternator brace to a 4 bolt style.