The much anticipated Ultra "Street" Intake Manifold for the '02-'05 Civic Si and '02-'06 RSX/ RSX Type S, and/ or any swa The Ultra Series is years of research and development, culminated in a multi-piece cast aluminum intake manifold that offers advantages that only a modular design could allow. Using the latest in CFD (Computational Fluid Dynamics) software; Skunk2 Racing has created a two-piece modular design that allows for easy disassembly, porting, and plenum volume changes through the use of a removable plenum lid and optional plenum spacers. In addition to CFD testing, the Ultra Series Intake Manifold has undergone extensive in-house dyno testing which has led to a design that is less restrictive, yielding both torque and power gains well over many of the competitors.p using the K20A/ K20A2/ K20Z1/ K24A1 engines or cylinder heads has finally arrived! Skunk2 Racing Ultra Street Intake Manifolds are cast-aluminum, manufactured from high-grade 356 aluminum alloy for strength and lightweight. Each manifold is CNC-machined for a precise fit, and individually inspected for quality assurance. The Ultra Series Street manifold features a generous 71mm throttle body opening and is constructed with thick walls at entry, minimizing concerns of breakthrough when port matching. Intense planning and design went into the plenum to distribute even airflow to all four cylinders under dynamic load conditions. Placement and design of the velocity stacks were rigorously flow tested to ensure maximum delivery of air to the cylinder. Large velocity stack raised bell mouth entries lead to 6.85” long intake runners with smooth transitions allowing the Ultra Street Intake Manifold to really move some air! Skunk2 Racing Ultra Street Intake Manifolds are designed to be used in modified naturally aspirated applications as well as mild turbo/supercharged setups. The K Series Ultra "Street" Manifold uses the EARLY PRB/ PRC style cylinder head and throttle body mounting flange pattern but can be installed on the LATE RBC/ RBB style cylinder heads through the use of an aftermarket Water Bypass Adapter and our DBW Throttle Body Adapter (PN# 309-05-0120)