Scientific Rabbit Big Bore CIS Lower Air Box Kit


Unlock the breathing potential of your factory CIS injection. The original 8-valve CIS lower air box is restricted by a 2.25" inlet, bottlenecking your intake flow. This 3D-printed big bore kit upgrades the entire cold air path to a full 3" diameter without requiring any modifications to the delicate CIS fuel distributor.

We’ve also eliminated one of the biggest headaches of the factory CIS system: the spring clips. The upper and lower sections are now securely sandwiched together using M6 studs and custom hold-down brackets.

Key Features:

Massive Flow Increase: Upgrades the factory 2.25" inlet to a full 3" diameter for improved engine breathing.

True Cold Air Routing: Includes a 3D-printed 3" lower elbow that mounts in the stock location under the radiator, drawing in cool air.

Zero CIS Modifications: Fits perfectly in the factory location. Your original upper CIS assembly and air filter bolt right on.

No More Spring Clips: Replaces the frustrating factory retaining clips with a secure, frustration-free M6 stud and bracket mounting system.

Engine-Bay Tough: Constructed from high-temperature, 3D-printed ASA components designed to survive extreme under-hood heat without warping or degrading.

 

Inlet Size Comparison:

Scientific Rabbit Big Bore: 3.00"

Audi Aluminum Air Box: 3.00"

Factory 16-Valve Box: 2.75"

Factory 8-Valve Box: 2.25"

 

Want to see the data? Check out our Research page for real-world dyno test results comparing the factory box to our big bore lower intake!

 

$225 + Shipping
(Please use the contact page to place an order)

 

What’s Included:

3D-printed big bore lower air box

3D-printed 3" front cold air elbow

3" connecting intake hose

M6 mounting studs and hold-down brackets

Air box modifications have been part of the minor performance upgrade list for a while.  Now easier and cleaner to upgrade with this kit.

MK1 AEG Manifold Swap Cold Air Box

MK1 AEG Manifold Swap Cold Air Box

Engine swaps bring reliable, modern power to the MK1 chassis, but the finishing touches are often the hardest part of a custom build. Don't let a generic pod filter soak up hot engine bay air and rob your engine of performance.

This custom air box is designed specifically for MK1s running an AEG intake manifold (whether on a full MK4 2.0 swap or an ABA block). It provides a true cold air solution that looks OEM+l, utilizing the original MK1 CIS air box mounting points and the factory under-radiator cold air inlet.

Key Features:

True Cold Air Routing: Includes an upgraded 3" elbow and flex duct to draw fresh, cold air from the factory lower inlet.

Drop-In Mounting: Bolts directly to the factory MK1 CIS air box mounting locations—no drilling or cutting required.

Precision Airflow: The lid outlet points directly to the passenger-side AEG throttle body and features the exact internal diameter required to keep your ECU happy.

Built for the Engine Bay: Manufactured from high-temperature ASA to easily withstand extreme under-hood heat without warping.

AC Compatible: Designed with the clearances needed to fit alongside factory air conditioning lines.

What’s Included:

  • Custom lower box and upper lid with M6 studs

  • 3" lower cold air elbow and connecting flex duct

  • New high-flow air filter

Note: MAF sensor is not included. Your factory ABA or MK4 MAF simply slides in and bolts onto the new lid.

 

 

$225 + Shipping
(Please use the contact page to place an order)