When sourcing LS intake manifolds, you must prioritize material composition and runner length. Aluminum manifolds are preferred for high-boost applications due to their burst resistance, while composite/nylon manifolds offer superior heat soak resistance for street performance. Ensure the flange type matches the cylinder heads (e.g., Cathedral Port, Rectangle Port, or Square Port/LS7). For high-RPM power, look for short-runner designs, whereas long-runner designs are essential for maintaining low-end torque in heavier vehicles.