Is a warranty voided if you remove the tab inside the stock exhaust pipes on a Harley Davidson motorcycle to make them louder?

Depends on the dealer. My dealer wouldn't care, but other Harley Dealers might. But to answer your question yes it probably would void your warranty. Also remember if you do a stage one or even a big bore kit that also voids it too.

Actually if the stage one kit or big bore kit the warranty stay intact AS LONG AS a harley dealer service department installs it, any factory accessory keeps warranty intact