A 1997 or 1998 FICHT has injectors that screw into the cylinderheads and have a very large locknut around them. The 1999 injectors have an oval flange with 2 bolts holding them to the heads. In addtion the '99's have a water cooled smooth ECU compared to the finned air-cooled ECU from the earlier models.

Look at the sparkplug indexing article in ONE STOP SHOPPING and there are pictures of the updated pinned cylinder heads and a sparkplug chart.