I looked around for a while trying to add a fuel composition sensor to my 0411 running my L31 and finally found a way. I have been using these for a while with the Mexican GMT800 L31 tune. Operating system is the same as most 2005 GM trucks, 12592618. Just have to run a DBC PCM and on a GMT400 based truck or van also need to convert the AC to analog cycling setting. Can run flex fuel by adding the sensor and adjusting the settings. Currently have the 383 in my 97 Express van setup with a 4L85E trans segment and Flex Fuel sensor. Just felt like passing on the Mexican GMT800 L31 tune. On my previously 0411 swapped van, all I did was unplug the PCM, swap the red plastic connector ends for green connector ends and plugged it in. Have to disable all the 02 sensor heater circuit codes since the L31 harness grounds the heaters externally, but otherwise my stock 02 sensors on my 97 van worked with the Blue/Green PCM. Also need to disable the oil pressure option in the system options since the older L31 does not use the oil pressure transducer. I added the pcm alternator control wiring using a diagram for a GMT400 8.1 truck. The tune attached is the unaltered L31/5spd GMT800 Mexican truck.
1MBL31.hpt