Hey guys , I know there’s tons of threads out there related to these issues , and I’ve read about every single one of them trying to figure this out. On my 97 fzj80 I have the p401 that I can’t get rid of. I have tested the egr modulator, tested the egr valve , did the VSV mod using the dorman 911-850 VSV, cleaned and replaced most vacuum lines and nothing is solving the CEL , the modulator was replaced by the last owner and is basically new , everything’s cleaned , the trucks only got 165k , any tips would help, I’m not sure whats left that I can do !!