After discussing my exhaust mod with a few guys,I may have to make some mods to my modified cats. Seems if you just gut them out,you end up with more of a restriction than with the functional convertor. The exhaust gas will expand into the empty chamber,then have to funnel itself down again to exit into the 2 1/4 inch pipe. This is probally more critical at the first pair of cats. Will have to pull it and re engineer.