LSXRT - Injection Molded Polymer Intake - Cathedral-Port Head Equipped Applications Designed specifically for GM 4.8/5.3/6.0L cathedral port cylinder head-equipped truck engines and cathedral port LS1, -2, -6 applications where hood clearance is not a concern, the FAST™ LSXRT™102mm Intake Manifold follows the path chartered by the original FAST ™ LSX™ Gen III Intake by featuring a modular design that allows for easy porting and disassembly and a runner design that yields an incredible 25 peak horsepower gain over the stock intake, on a stock 6.0L engine with a Big Mouth 102mm Throttle Body™. Extensive testing led to a runner design that is longer and less restrictive and gives the user the ability to remove individual runners from the manifold for modification. The LSXRT™ is constructed from a proprietary precision injection molded polymer which offers many benefits, including lighter weight, greater strength and lower heat soak propensity. While it features a 102mm air inlet that was designed for the FAST™ Big Mouth 102mm Throttle Body™, it can also be used with OEM electronic 78/90mm or aftermarket 90/92mm throttle bodies (three-bolt electronic throttle bodies require an adapter). Other features include integrated nitrous bungs and a precise bolt-on fit that permits the use of factory accessories and OEM fuel/emission connections without adjustments or clearance issues. 25 HP gain when used w/ 102mm Big Mouth Throttle Body™ on a stock 6.0L truck engine. Constructed from proprietary precision injection molded polymer; Lighter than aluminum w/ lower heat soak propensity & greater strength over stock molded intake. Innovative multi-layer design w/ removable runners for quick & easy disassembly & porting. Integrated nitrous bungs; plug-and-play w/ ZEX™ LSX™ Direct Port Nitrous System. Patented Design - U.S. Patent No 8,567,366. Throttle Body Options FAST™ 102mm CNC Throttle Body2 (Drive-by-Cable)3. OEM/Stock 3-Bolt Throttle Body w/ FAST™ Adaptor Plate. OEM/Stock 4-Bolt Throttle Body. Fuel Rail Options FAST™ Annodized CNC Fuel Rail Kit4. OEM/Stock Round Plastic Fuel Rails w/ FAST™ Adaptor Kit. OEM/Stock Square Metal Fuel Rails w/ FAST™ Adaptor Kit.