Got a question for all you gear heads and mod warriors. Is it feasible to just replace the exhaust down pipe(flex pipe) as a stand alone mod? I was considering getting ported exhaust manifolds, but for the price and effort was a bit standoffish. What if I kept my exhaust manifolds in place and only replaced the down pipe with a ported one? Will this gain me any HP or do anything at all?

Perhaps this should've been in Performance and brainstorming....

Your stock exhaust flows pretty well. Unless you open up the manifolds (your restriction) anything else down the line is pointless.