What's the best bang-for-buck intake manifold for a stock-motor LS1?

The stock LS1 intake is the weak link among factory LS intakes, so almost any factory upgrade helps.

• LS6 intake (or Dorman's copy): long a quick upgrade worth 15-plus hp on a hot-rodded LS1. GM stopped making it; Dorman's replacement made nearly the same power as the original in a dyno test.
• TBSS intake: the best-performing factory cathedral-port intake, but tall — often a no-go on low-hood applications.
• Aftermarket short-runner intakes add top-end power but can give up torque through much of the curve. Match the intake to the rpm range you'll use.

The gains are smaller on a stock engine than on a modified one: the more the rest of the engine flows, the more a better intake adds.