SnowDrift is using the boost solenoid connector to grab 12v. ign.
He is using mechanical boost control, so no longer needs that conn.
The FSO would work for a relay trigger but I would stay away from
any IP circuits, there are other better choices.
The mate to the boost sol. conn. is 12162000.
Pigtails are - PT786 12167120, PT2373 88862292, AUVECO 23190
There are a few on the truck.
The underhood light has one.
U-pull-it - many GM cars and trucks.
All the connectors on your truck are GM/Delphi/Aptiv.
The pink wires to the GPR, or FFM or boost solenoid would work.
What are you using the 12v. for?
Any other 12v. ign under the hood I would not tap into.
Unfortunatly there is no auxillary 12v. ign. tap under the hood.
There are some in the convenience center in the cab.
The old RY139 GPR was self controlling and is used on mechanical IP rigs, has 4 terminals, black conn.
The new RY383 GPR is PCM controlled and is used on DS4 IP rigs, has 3 terminals, grey conn.
Both connectors have 5 term. spaces and look the same but are keyed different and will not interchange.