Interesting...
So it was giving a clean signal, and then you switched to E50 and it became erratic?
I'd suggest NEVER using VE auto tune - further to this, its being dropped in the new firmware releases.
Try turning the EGO feedback off and map the fuel at idle, use your ears more than relying on the lambda at this stage, when you get a clean idle then check the lambda reading - it should be good and steady.
You're going to have a fair amount of tuning to do with E50 - it has the potential for a wholesome amount of power.