The 3 codes are for all models having the ITT Mark 20 IE Controller
ABS only =03504
ABS and EDL=13504
ABS+EDL+ASR =13204

Which functional block are you referring to? I can take a peek. All of the logical elements are defined at the start of the FR

Maybe we can start tracing the whole process?

I'd like to disable ASR

no intervention problems, I'm wanting to tweek ASR instead of just disabling it.

it is in the ABS controller. In my experience with ASR, especially when trying to launch off the line, it slams the brakes so hard to stop the wheel spin that the engine bogs and then ECU kills the power. If you leave it @ WOT its like you are riding a bucking bronco as power comes back in and out while wheels spin then get stopped. Sometimes it engages and the traction light blinks repeatedly as I roll forward a few feet before the engine gets power back and does it all over again.. I wish to be able to keep it @ WOT and ASR slowly engage brakes to the wheel with most wheelspin to slow it down instead of stopping it. I want ASR to control where the load gets distributed during wheelspin instead of just stopping the wheelspin all together but also keep the wheels as close to the threshold of braking traction as possible without crossing over too much. you know.. true Anti Slip Regulation...

I have noticed that using different brake pads change the performance of ASR. A stock compound pad or one for high durability keep ASR way numb compared to more aggressive pads like for racing or even high performance street pads. I've used hawk brand and it sucked. R1 kevlar pads and it sucked.. napa brand oem pads were as expected and Everwear or something like used some super long durability pads from Advance auto. They had a 2 year free replacement with unlimited mileage. ASR worked better than oem.

I also installed the larger diameter Audi TT rotors to my GTI and ASR seems to have improved somewhat again. I think because they are heavier.

I'm sure there is a way to hack the controller but don't know if the ABS pump itself is capable of performing like this. It might could only be an on/off kinda deal. I think the pump would have to be able to operate sequentially so that amount of pressure applied to the brakes is adjustable.

So you really think software intended for use on Bosch Race ABS could be used on your stock ABS system?

I had the same symptons as you describe "when trying to launch off the line, it slams the brakes so hard to stop the wheel spin that the engine bogs"

When it did engage, the traction light blinks repeatedly.

When I recoded the brake controller for "ABS only" it eliminated the "slamming and bog down" aswell no light on the dash and non functional ASR switch.

I have steel braided lines to all four brake calipers which elimiates the spungy feel in the pedal and improved braking power. of course I flushed the system, put new fluid and re-bleed the whole system for air, along with the clutch master and slave cylinder. As recently had those items apart for fresh 02J transmission swap, which I wish now I invested in 02M, but with the 02J I like B&M short shifter with the reverse lockout, which is not available for 6-speed, with Sachs stg2 228mm flywheel and clutch kit. All other transmission hardware is new, nuts, bolts, wiring, etc.

I have no slipping in anyway on the clutch or gas pedal with the ABS recoded for ABS only and now have no symptons such as you described. Everything grabs and performs well with a good tuning. A bigger brake rotor and caliper size would be my next option aswell, vented and slotted rotors and bigger pin kit for the calipers.

I would like to give that adjustable ABS sw that you found a try when I have some free time to do so and will report back if I find any other ways to mess around with ASR system in the brake controller.

not sure what the 2.7t cars get but the mk60 abs system has different softcoding than the mk20 iirc.