LLY duramax rough idle in park hot
 

Got a 2005 duramax. All stock except: s&b intake, 3" downpipe, 4" straight pipe, afe turbo mouth piece, head studs, EGR delete.
Truck runs fine until engine coolant reaches 160 degrees. Once past 160 degrees, calculated fuel rate drops off to 2-4 mm3 and gets a surge/Lopey idle heard in the tail pipe.
Demanded vs actual fuel rail pressure is within 100psi.
When this happens, injector balance rates all go to 0's.
Truck has new injectors and a Fpr.
Injector harness has been ice picked.
Wires at alt bracket have been checked, all good there.
As soon as you put the truck in gear it smooths right out and calculated fuel right comes right back up to 10mm3.


Not sure where to look next.
Thanks in advance.