misfire

I had a misfire on cylinder 5 i replaced the intake and plenium gaskets and still got a rough idle and miss any more suggestions took it to the dealer one day after gaskets replaced and he told me it was the intake and it takes 6 .5 hours he full of shit the book says 3 hours help thanks could it be injectors or map sensors ect

found problem number 5 injecxtor bad problem solved