F.A.S.T.’s LSXRT Injection Molded Polymer Intake


Modified LSX-powered trucks are all the rage these days, and with companies like FAST onboard with making the hardware guys (and gals) like us need, they’re more than happy to fill a niche that others might not be able to.

Enter their LSXRT injection molded intake manifold – it’s perfect for cathedral-port headed 4.8L, 5.3L and 6.0L GEN-III engines requiring increased airflow, maximum horsepower & torque, and the provisions for nitrous!

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 SystemLSXRT
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