u dont need the rear cats... for ur 93 diablo... it dosnt make it very laod but it becomes more deeper sound.... just get ur self the mufflers . or a cat back system to start...

i always like the borla system.. i had it on my old 91 and it was incdredible... even had some back fire when i was down shifting..

but i never liked the end pipes on the borla. they were not realy good on the eyes... but the sound was amaizing

hope that helps