@Hondasxs What year is your Dodge Ram pickup? An exhaust leak ahead of the catalytic converter output is an emissions issue.
I haven't paid much attention to emissions warranties because I haven't experienced a related problem but I think all manufacturers now provide a 5 year warranty on emission control equipment. Your issue could possibly be under warranty.
Replacing a factory exhaust manifold with a header violates federal emissions rules on vehicles with a catalytic convertor UNLESS the header manufacturer or distributor has obtained an executive order certifying the header. There's a reason for this. Headers typically flow better than exhaust manifolds which alters combustion, fuel burn, and emissions.
The following list will help you determine if a part for your vehicle is a replacement part and legal for use on pollution. Check the manufacturer's catalogue to verify vehicle application and look for disclaimers, such as "Not legal for street use in California."
ww2.arb.ca.gov
Califonia is, of course, the wackiest and most restrictive of all, but their requirement is generally the rule in the democrat-controlled states where emission-testing is a requirement for registration renewal. If your state doesn't test it's not an issue.