Is a FAST intake worth it on a bolt-on LS or cammed C6? Vengeance Racing back-to-back dyno results.

It depends on how modified the engine is. We don't have the Vengeance Racing data, but OnAllCylinders ran a similar back-to-back:

• Test: a cammed 5.3 L33 (BTR Red Hot cam, springs, long tubes), stock truck intake vs a FAST LSXR with a 102mm throttle body.
• Result: 456.5 hp → 480.7 hp (+24 hp peak) and 411.7 → 416.7 lb-ft. Most of the gain came above 5,000 rpm; below that the two intakes traded a lb-ft or two.
• Why: the FAST optimized power in about the same rpm range as the stock manifold, just more of it. Many short-runner intakes add top-end power but lose torque through much of the curve.

The rule: the more the rest of the engine flows (cam, heads, displacement), the more a better intake gains. On a stock or bolt-on engine the gain will be smaller than on a cammed or stroked one.