"XL" Group. A Battle Garage and Martelius Collaboration Header 

Suits 16V and 20V 4AGE's in LHD and RHD layouts (even with power steering)

• This is the more muscular version of the fast road Group. A header we offer -  Ideal for GZE, 7AGE, and modified 4AGE engines
• 4-2-1 design developed for competitive rally events enables broadest power band
• Long secondaries promote a strong mid-range without choking the top-end
• Optimized for engines outputting between 150 - 215 bhp or up to 240 hp GZE
• Spec'd by Battle Garage for our customers with O2 sensors in the factory position - no extending of the O2 sensor wires needed! Extra wideband O2 sensor bung included as well  
• Bolts up to catalytic converter in factory position, if desired.
• Stainless Steel construction for longevity. 
• Now clears factory oil filter location and oil filter adapter blocks
• 42mm Primaries -> Long 47mm Secondaries -> 57mm / 2.25" collector

This header has been designed to get as much power under the curve as possible while still letting the engine breathe up high.  This is important for hill climbs, rally, drifting, and even street driving (in areas without pollution control of course) as the car can go from falling flat on it's face at 3K rpm, to pulling well with a properly spec'd header. For instance, some may have noticed that after installing any one of the commonly available 4-1 headers, the car was much weaker than stock below 5K rpm, and maybe pulled a bit better up high.  Maybe.  Or, a 4-2-1 header was purchased, but the tubes were far too large, secondaries too short, and the car still was dead below 5K? Exhaust primaries and secondaries are critical, folks.  Just trust us when we say that this is a pretty good starting point for people wanting the most overall power out of their modified 4AGEs, 7AGEs, and GZE engines.

Note: To give the user the option of using either the factory O2 sensor, or the wideband O2 sensor, two sensor ports are provided. The factory O2 sensor port can easily be opened up with a cordless drill before use.

OEM 16V Exhaust Hardware can be found here.