[rmjdrift]

Aftermarket headers can improve exhaust flow by improving the header design and diameter. Basically allow the engine to exhale more freely and gain power.

Yes the Tundra has stock headers and they are a great design, JBA and Doug Thorley have made improvements (based on the dyno charts) but by the experience Hava had, i don't know if it's worth the effort

There are great gains on the Intake and Exhaust alone and those are rather simple upgrades