Tuning your Subaru in a post Greenspeed era With a Cobb Accessport

As I write this article it has been over two and a half years since Cobb pulled the plug on their original flex fuel. With that they began the process of introducing new EPA compliant Tuning software and new hard parts like flex fuel and fuel pressure sensor kits. You may hear the terms “Greenspeed” or “NexGen” thrown around a lot. Those basically refer to Cobbs’s commitment to sell EPA compliant parts and software.

When Cobb first pulled the plug on flex fuel it was a very confusing time. Was this the end of flex fuel for good? What parts can we and can we not have installed now when getting tuned with a Cobb Accessport? After several years of hard work Cobb has re-introduced flex fuel support for a large range of vehicles. Not everything is supported anymore but the major models and years are supported.

Current Vehicles with full Flex Fuel support (including either Fuel Pressure Sensor or 1 External Sensor) are:

2008-2021 STI
2015-2021 WRX
As of 11-26-2024 it is rumored flex fuel will be available for the 2022+ WRX and at some point, maybe the 2008-2014 WRX.

With the removal of the original flex fuel Cobb also removed the ability to disable certain check engine lights. With over 2 years of tuning vehicles with all emission parts installed and working I have to say that power is basically the same as it was when people were removing TGV’s. Removing the air pump system was something that was done as well with kind of remove it before it breaks mindset. Air pump system failures are few and far between at our shop so removing them wasn’t stopping a part from failing as they rarely fail.

Here is a list of codes that can no longer be disabled and the system has to be fully functional in order to be tuned via a Cobb Accessport. This applies to all Subarus including 2002-2024+ WRX, 2004-2021 STI, 2004-2018 Forester XT, 2005-2012 Legacy GT / Outback XT.

Catless Exhaust – Codes: P0420.
- I think this has been the hardest one for people. Installing a high flow downpipe was typically one of the first mods done to a Subaru. With over 2.5 years of tuning cars with Cats that don’t throw codes I can say the power is almost the same if not the same as previous generation catted downpipes. The only Catalytic Converters we have seen not throw codes are the GESI branded units. If your downpipe has a Catalytic Converter other than a GESI brand you will have a high likelihood of throwing codes if tuned on the latest software. The older cars 2002-2007 aren’t as picky on what cat they need but as you get newer the ECUs get more advanced and require better and better aftermarket Catalytic Converters to not throw codes.

Tumble Generator Valve or more commonly known as TGV – Codes: P2004, P2005, P2006, P2007, P2008, P2009, P2011, P2012, P2016, P2017, P2021, P2022.
- This system needs to be installed and working. This system was commonly deleted as a performance mod. As we have been tuning cars with fully functional TGV systems, we have found them to make the same or almost the same power as its deleted counterpart. That means you are not really losing any performance having this system working. Some TGV codes can cause the car to go into limp mode where either the boost control system is disabled or it can cause feedback knock to read -5 deg at any engine condition except idle.

Air Pump or Air Injection System – Codes: P0410, P0411, P0413, P0414, P0416, P0417, P1410, P2257, P2258, P2431, P2432, P2433, P2440, P2441, P2442, P2443, P2444.
- This system was commonly deleted as a way to potentially lower repair cost if any part of it failed. There were never any performance gains from deleting the Air Pump system. We actually very rarely get cars in the shop with Air Pump problems. Even before Cobb removed the ability to delete this system, we were not deleting it on 2019+ STI’s as it was needed for the car to run properly on cold starts. If you have P2431, P2432, or P2433 codes you are likely missing your Barometric Pressure sensor. That sensor is housed in part of the Air pump system and having it not installed can cause the car to have idle and other drivability issues.

Rear O2 Sensor – Codes: P0037, P0038, P0137, P0138, P013A, P013B, P013E, P013F, P0140, P0141.
- There was NEVER any performance gain from deleting this. It was deleted if you had removed the Rear O2 or were using the Rear O2 as an input for the ECU. With Cobbs new software there is absolutely no need to have your Rear O2 removed.

Evap System – Codes: P0441, P0451, P0452, P0453, P0455, P0456, P0458, P0459, P04AC, P04AD, P04DB, P1400, P1420, P1449, P1451, P2401, P2402, P2419, P2420.
- This includes things like EVAP Pressure Sensors, EVAP Leaks, EVAP Purge Valve, PCV, Fuel Tank Pressure Sensors, EVAP System Clogs, EVAP Switching Valves. There was NEVER any performance gain from deleting any of these components.

EGR or Exhaust Gas recirculation System – Codes: P0400, P1492, P1493, P1494, P1495, P1496, P1497, P1498, P1499.
- This system was commonly deleted in hopes to lower the likelihood of getting carbon buildup on the back of the intake valves. We have found having an AOS (Air Oil Separator) can have very similar effects. The Cobb units are 50 state legal so you can install one regardless where you live in the USA. There was NEVER any performance gain from deleting any of these components.

EGT or Exhaust Gas Temperature – Codes: P0545, P0546, P1312, P1544
- This was deleted when a catless up-pipe was installed on the 2002-2005 WRX or 2004 Forester XT. If you want to be tuned with an Accessport on these vehicles you will likely need an up-pipe with a working EGT sensor.