What is the EFI store telling you? They are a dealer and teach the classes on install, tuning, troubleshooting etc.... they should have another HP unit to change out to see if its cabling or the ECU...

I have ran the Dominator efi on my ls turbo car for years now without issue. I am cuurently installing 2 terminator x units for lsa superchargered ls3s. If you really think it is a bad box I would without a doubt send it in especially if under warranty.

Holey made good on it. There was a corrupt file in the programming. They fixed the internal error and it works as prescribed.