AMS Performance Subaru WRX / STI EJ Intake Manifold

Introducing the AMS Performance Subaru EJ Intake Manifold — a no-compromise solution for serious power and the highest horsepower-producing manifold in its class. Designed and tested in-house using SolidWorks® and CFD analysis software, this cast manifold features a massive 4.5-liter plenum, 13” equal-length runners, and 2.5” tapered ports for maximum airflow and efficiency. CNC-machined bellhorns act as internal velocity stacks, delivering a broad powerband and impressive top-end performance. In dyno testing, we saw gains of up to 51 WHP over the OEM manifold. Available in standard or reversed configurations, it supports throttle bodies up to 70mm (with mild porting) and is compatible with top-feed injectors and aftermarket rails. As the most cost-effective intake solution at this power level, it’s the perfect choice for racers and enthusiasts looking to get the most out of their EJ engine.

Engineered To Be The Best

Unmatched power gains and excellent response

To validate the performance gains of the AMS Subaru EJ Intake Manifold, we conducted extensive back-to-back dyno testing across multiple vehicle setups. Each test was designed to isolate the manifold’s impact by comparing identical configurations with and without the AMS manifold installed. The results were clear: significant increases in power and throttle response across the board. On a 2007 STI equipped with an AMS Rotated Kit, PTE 6266, GSC S2 cams, ported heads, and Supertech +1mm valves running 93 octane, power jumped from 470 WHP to 521 WHP—a massive 51 WHP gain. Even on a more modest builds, like another 2007 STI setup with a GT30R turbo on pump gas saw power rise from 396 WHP to 410 WHP. Similarly, a 2008 STI with a PTE 5858 turbo gained 10 WHP, increasing from 398 to 408 WHP. These results confirm what we engineered this manifold to do: deliver broad, usable power gains throughout the RPM range. Whether you’re chasing lower lap times or faster quarter miles, the AMS EJ Intake Manifold gives you the boost in performance to pull ahead—where it matters most.

Applications

• 02-05 Subaru WRX w/ EJ20 (Requires adapter to use WRX style drive by cable throttle body)
• 06-07 Subaru WRX w/ EJ25
• 08-14 Subaru WRX w/ EJ25 (Requires using STI style drive by wire throttle body)
• 04-Current Subaru STI w/ EJ25 (2008+ STI may require mild clearancing of A/C compressor line)
• Will fit various Legacy and Forester EJ25 applications with proper throttle body usage and custom fitting

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