cutting out at 50 mph

[money pit]

I have a 04 duramax.with a over sized injectors and efi live with a built transmission.it just started cutten out at 50 mph under hard acceleration,i have to lift up and press back down to get it to go over 50 mph.was wondering if anyone has any ideas on what it could be.

[Kennedy]

Check for trouble codes first.

LB7 or LLY

If no codes try holding pedal down until light comes on.

Oversize injectors plus tuning can create all sorts of complications.

[More Power]

I'd change the fuel filter as a first step. Ordinarily, a low rail pressure due to a fuel restriction will set a code, but not always... Jim