Skunk2s engineers went back to the drawing board when they set out to improve the already popular 06-11 Civic Si’s RBC intake manifold. Each of Skunk2’s Pro Series Intake Manifolds for Honda’s K-series engines feature larger plenums and shorter, oversized runners when compared to the RBC, and are cast with thicker wall material, leaving room for further porting for high-horsepower applications. Instead of producing a manifold with a significantly oversized plenum and excessively short runners that would sacrifice mid-range power, Pro Series manifolds were designed for the “street enthusiast” who wants more power but doesn’t want to sacrifice mid-range performance to get it. The results are improved airflow, an enhanced venturi effect, and both mid-range and top-end power gains. Skunk2’s all-new, cast-aluminum Pro Series Intake Manifolds for Honda’s K-series engines are a direct-fit replacement for all 06-11 Civic Si engines thanks to their unique design and throttle body flanges, which are compatible with OEM throttle bodies as well as those as large as 76mm. A thermal-insulated intake manifold gasket is also included, making for a truly bolt-on installation (no drilling or modifying required). Pro Series manifolds also incorporate an angled-runner design, which allows for ample hood clearance on almost any engine combination. Pro Series Intake Manifolds offer horsepower and torque gains greater than the popular RBC manifold but without compromising mid-range power output. The design incorporates runners that are similar in length to the RBC’s but with larger bores, a special tapered design, as well as a larger, tapered plenum that together preserve mid-range power but increase and accelerate airflow to allow for significant top-end power gains. Pro Series Intake Manifold runner exits are also machined and hand-finished to best match the cylinder head’s ports.This Part Fits: Year Make Model Submodel 2004-2008 Acura TSX Base 2008 Honda Civic MUGEN Si 2006-2011 Honda Civic Si