Yeah i think from 96-98 they had a Boss Mustang. And they might had a few new edge mustangs. Closest thing i can think of that he is talking about is on their website for the 05 protype.
http://www.teamshinoda.com/ I never heard of any in the early 90's. They had them late 60's and early 70's and i am pretty sure 96-98. Pretty much just Graphics..chin spoiler, fender flares different spoiler..mostly an appearance package. The fast ones were the rare boss cobras, they were supercharged. Rumors was they were gonna make a new boss in 04, like they did with the mach, but never happened. Rumors has it now in 06 There is gonna be a new shelby mustang. I know he is back to working with Ford now, i.e the new shelby cobra. I cant wait to see that mustang if it happens.