Do these require a modded ECM?
Yes they do require a ecm that is modified.
Low ohm value or low Z as it is refered to sometimes require the injector
driver circuits in the ecm to be modified to handle the higher current that
the low z injectors draw.
Some have used non modded ecm's successfully but it is not recommended.
The low z injectors respond to the ecm pulses better than a high z injector of the same
fuel flow rating once you get into the bigger sizes....55# and up normally.
Although in the last few years the higher flow injectors that are high Z are getting better
and as a result of that it is driving the price down of the low z injectors like I have for sale.
If you have a modded ecm or a fast system these injectors and the others I have listed
for sale are a bargain compared to what I paid for them new.