'90-'91 and '92-'93 are different. Some catbacks will come with an extension (the cat is smaller) for the '92-'93, some sell it as an option, some don't at all, some make separate systems.

The options that I've seen:

DC Sports; for '92-'93, too long for a '90-'91
GReddy MX; short enough for '90-'91, comes with extension for '92-'93
HKS Hiper; separate systems for '90-'91 and '92-'93
Tanabe Super Racing Medallion; short enough for '90-'91, extension for '92-'93 sold separately
Tanabe Super Hyper Medallion; short enough for '90-'91, extension for '92-'93 sold separately