The ULTRA is equipped with a supercharger. Before 1996 it was possible to get the supercharged motor on a "non-ultra" vehicle. Prior to 1996 it was a trim level only. After 1996 the ULTRA carried the supercharged engine as part of the ULTRA package.
I am not certain if this was a half-year change or not
The Ultra was a higher trim level than the park ave. Also most if not all Ultras were supercharged..........UJN