I recently bought a turbo truck and I've been going through the tune to try and increase the MPG since it only gets about 10mpg.

I've been fighting DFCO and have been having problems with it. I can get DFCO to enable, but it disables after about 2 to 3 seconds because the RPM of the truck is falling below 400 rpm (I have it set to disable at 400) when DFCO enables while cruising between 50 and 60 mph. Is DFCO not possible with a loose converter or could something else be causing the major RPM drop? I'm running a 4L80E with a Precision Industries 3800 stall.

Any help would be appreciated!