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AMS Performance Intake Manifold 2004-2021 STI

SKU AMS.31.08.0002-2
Original price $1,299.95 - Original price $1,299.95
Original price
$1,299.95 - $1,299.95
Current price $1,299.95
Select Version: Reverse Rotation Coated

Stay Ahead Of Your Competition With The AMS Subaru WRX / STI Intake Manifold!

The AMS Subaru Intake Manifold was designed to outperform the competition. We referenced many modern design examples and engineering studies to bring you the best intake manifold available for the Subaru EJ20 and EJ25 WRX & STI. After extensive testing we ended up with a manifold that makes more power than anything else currently available on the market!



  • 4.5 Liter Plenum Volume
  • 13” Equal Length Intake Runners (Measured from Face of Bellhorn to End of Runner)
  • 2.5” (63.5mm) Intake Runner Diameter (ID of Bellhorn)
  • Bellhorn OD 3.8” (96.7mm)
  • Increased Port Size at Cylinder Heads Allow Matching to Larger Hand Ported or CNC Ported Cylinder Heads
  • Available in Standard or Reversed Configuration
  • Throttle Body Opening Accepts Larger Throttle Bodies up to 2.625” (66.675mm) or 70mm with mild porting
  • Available in 4 Configurations (Standard, Standard Coated, Reversed, and Reversed Coated

Product Notes

  • Due to the large variety of rotated turbo kits on the market, we cannot guarantee fitment with every brand. Depending on the turbo location and sizing, interference with the cylinder 3 intake runner is possible.
  • Some port matching may be required when used in conjunction with CNC or hand ported cylinder heads.
  • The intake manifold is available with a standard or optional reverse throttle body orientation, allowing for more direct intercooler pipe routing.
  • Larger throttle bodies can be used with proper modifications (Up to 70mm with minor porting) (Larger throttle bodies may also require adapter flanges)
  • The intake manifold is flanged for 04+ STI drive by wire throttle bodies, but cable throttle bodies can be used with custom fitting and flange adapter.
  • Standard configuration intercooler piping will need mild custom fabrication due to placement of throttle body.
  • Reversed configuration requires the relocation of the alternator and removal of the A/C compressor. Installation is not a direct bolt on and will require custom intercooler piping.
  • The intake manifold is designed to use a common Subaru aftermarket top feed injector size. (48mm overall length / 11mm inlet – standard Subaru rail size / 14mm outlet) We recommend the use of Injector Dynamics brand injectors.
  • Standard Subaru style injectors cannot be used. (Side Feeds, Stock STI Style Injectors)
  • Not compatible with side feed to top feed conversion rails
  • Requires aftermarket rails and lines, will not fit with stock
  • Not compatible with top mount intercoolers.
  • Not directly compatible with mounting the factory upper coolant reservoir. Custom bracketry will need to be fabricated to mount.
  • The bottom of the center plenum features four 1/8″ and one 1/4″ NPT ports for vacuum accessories.
  • 2008+ STI may require mild clearancing of A/C compressor line


Engineered To Be The Best

For the Subaru EJ Intake Manifold the plan was simple, take our years of engineering experience and design the best intake manifold available. Designed, prototyped, and tested in house by our team of Engineers, the AMS Subaru EJ Intake Manifold was created to be the best unit available on the market. By casting this manifold it is not only stronger, but it allowed us to optimize the power output by giving us the freedom to sculpt the interior geometry for maximum efficiency and airflow.
subaru ej intake manifold mods upgrade kit
AMS CNC Intake Bellhorns

By utilizing Solidworks© & CFD (computational fluid dynamics) software we started with an extremely large plenum size of 4.5L for the ultimate top-end power. We also designed CNC machined bellhorns which act as internal velocity stacks and allow for a broad power curve and high RPM horsepower capabilities. This allowed us to optimize massive 2.5″ tapered runners and matched cylinder port angles to minimize turbulence and maximize power output. The 13″ length of the runners allow for a smooth taper in cross section reduction, giving the AMS Subaru EJ Intake Manifold exceptional flow.

subaru wrx sti intake manifold
Designed in Solidworks


subaru wrx sti intake manifold mods upgrade kit
AMS Subaru EJ25 Intake Manifold in reverse configuration.
subaru ej25 intake manifold
2007 STI, AMS Rotated Kit w/ PTE 6266, GSC S2 Cams, Ported Heads, Supertech +1mm Valves, 93 Octane – AMS vs Stock
2007 STI, AMS Rotated Kit w/ GT30r, 93 Octane- AMS vs Stock
ej25 subaru intake manifold
2008 STI, AMS Rotated Kit w/ PTE 5858, 93 Octane- AMS vs Stock
subaru ej20 ej25 intake manifold mods upgrade kit
AMS EJ Intake Manifold in Standard Coated


Unmatched power gains and excellent response

This AMS Subaru EJ Intake Manifold offers more than just top end power. This manifold gives you an amazingly wide power-band with a huge jump in power whenever you are in boost. This equates to greatly improved lap times on the road course and the confidence to leave any opponent in your dust when on the drag strip!

Be the guy to beat, order your AMS Subaru EJ WRX / STI Intake Manifold now!