Likely ballast or ECU. take off the yellow "sol" wire from the starter relay to disable the starter & have a helper hold the key to "start" & w a VOM/test light you need fire at (1) the coil positive pri terminal and (2) 2 pins (if 5 pin ECU/1 pin if 4 pin ECU) at the pentastar ECU connector. Let key off to "run" & need fire the same on the coil but only 1 pin of the ECU, the "point" of the pentastar connector. Pull/ check/clean the bulkhead connectors EDIT less likely but check the pickup gap/ohm it if u can