When I installed my TRD dual exhaust I had the same issue with rust, so I just zipped them right off with a cutoff wheel. I went to Napa and bought the replacement bolt kit which came with all new springs, washers, etc., but no nuts. I don’t remember having to cut the nuts off the flanges, so they probably weren’t attached. I just ended up going to Ace hardware with the bolt and found a nut that would fit, and bought a couple to finish the assembly. No matter what you do, spend the $10, or whatever it was for new hardware because not only will it make your life easier, but having new springs will keep that flex joint working as designed. You can solid mount it if you want, but Toyota must have had a reason for putting a flex joint there, as opposed to solid mounting. Most cars have some type of flex tube in that area because of engine movement on the rubber mounts. My assumption is that over time, this will cause a solid pipe to crack. On my daughter’s Camry, there is a short section of braided stainless tube in that transition, and it recently failed, so now I have to either replace the whole thing, or see if I can find a shop to cut it out and weld a new flex coupling in.
