04 silverado SS. new build . engine will start and idle only. Cylinders 1,4,6 and 7 are not firing. Non DOD Engine. No signal to coil to fire. I have double checked coil grounds, ecm supplied ground and coil voltage supply. no herz signal to fire coil being delivered to these 4 cylinders. verified CKP sensor voltage. RPM is reading on tach and scan tool. Looking to see if anyone has ever encountered this issue?