could the injectors themselves be not working? have you tried repositioning the injectors on the fuel raile to see if they work in different spots? its a longshot but give it a try.

 

splice into the injectors negative terminal & do a straight ground see if that makes it work.

 

Reason I asked if you upgraded the wires is I have seen a few people who have had to upgrade their injector harness for big injectors (thought i heard you had 8* lb injectors.)

As for splicing into the harness to see if they are working I would rather get an injector tester (plugs into the harness and has a light that goes on and says if it is working or not. Usually costs about 70 bucks and up..

I have heard of a few people having problems with their ecu from fast and it only producing fuel for 6 cyl but I do not know if that is cause they had a grand national tune in there or something diff.

If you need to try out another set of large injectors i have a few sets. As well as some smaller 28's