LOL, wtf hahaha!

way over my head

 

soak the bolts in liquid wrench or wd40 even for a couple more days and then take the impact to it. Only problem is that I know the bolts you are having trouble with and the cat gets in the way of a wrench even so not sure if you are going to be able to get the impact wrench on them.

Also, you might be trying to take off the bolts that are actually welded/attached to the OEM cat so it's not going to come off without breaking. Put you wrench to the "nut", not the "bolt head"