No O2 sensors after the secondary cats. Only after the primaries - as long as you don't mess with those you're good to go as far as emissions are concerned.Looks good! There's no issues removing the cats? Isn't there an O2 sensor or something in that area?
Originally I wanted HCF's to replace the secondaries because I was gonna install primary downpipes with HFC's - I was concerned about overboost, so I figured having 2 sets of HFC's would prevent that. But since that's not happening, I think this will work just fine.