I don't have another K21/25 around here right now I did test the harness between the cam/crank sensors also replaced the Mass air flow with factory part, Checked the connectors at the ecm and relay panels no corrosion noted I will check the fuel pressure and see what I get also question maybe a dumb one but there is an inline plastic clear fuel filter is this an oem part or mechanic added @ 55 psi I would think it would be a different style filter but... I have seen more odd stuff

Thanks