That is a Mark DiGrappa designed and manufactured X-Brace, later distributed by Rick Hesel (aka Ricks Leather Accessories). No need to remove for oil change if you use a pan.
In the early days of the car Spoon came out with an X-Brace; which was Spoon priced. A college student at Pepperdine University designed his X-Brace. His name was Richard Ming (aka Mingster here on the board). He later founded his company Import Developement. I at the time was working in aerospace and had access to some rather advanced equipment to map relational displacement using piezo electric accelerometers. I had done a baseline on Spoon when Mark, who lived in Las Vegas, approached me to test his. His was much stiffer which did not make sense to me as Mark’s was 6061-T6 Aluminum where as Spoon and Richard’s we’re both mild steel. To this day I don’t understand the data but my chassis is stiff as all get out. I consider this one of my best mods in my 17 years of owning my ‘01. And that is saying a lot. It will never be available again as it is cost prohibitive to manufacture. unless someone can find someone who works at a super cool company who let’s you use idle equipment to make car parts as Mark did. Not sure how he upped the volume for Rick’s(.?). When S2Ki grew it became more profit based which all growing enterprises tend to do. Mark was only selling a few pieces and did not wish to pay the entry fee. I sent him Ricks direction and Rick took on the product. About the same time, and for the same reason, “Voodoo Bob” Krueger ended up going through Rick’ as well. Sorry for the ramble but wanted to share some board history. Trust me you have a rare awesome item on your hands.

Utah
P.S. Thanks for the memories!
P.S.S. The brace in the link appears to be one of Richards; not a DiGrappa/Ricks