'91 ZR1 different Mufflers and Control Arms?

[bradd15]

My apologies if this is a dumb question but I have been looking at 90-92 years and I noticed in the underbody pics of a few '91's some have the rectangle muffler and some have the double pipes on each side.
Also, I see some control arms are black and others are silver.
Was this an option or part of a package or color combo?

Thanks for the information.

Brad