I needed to do an engine bay in a Mustang in exchange for wedding photos. I used Easy Off oven cleaner and a pressure washer. The oven cleaner removed the Ziebart rustproofing that had been there since '67, took off all of the paint and primer to the bare metal!! It did not harm any plastic or rubber parts, just make sure you cover places you don't want it to go, like down the cowl vent. Did this one while the engine was in the car, and it cleaned up everything! Spray the oven cleaner on and let it sit for 5 minutes or so. DO NOT let it dry on. BE SURE TO WEAR EYE PROTECTION ( GOGGLES !!) AND A FACE SHIELD !! COVER ALL EXPOSED SKIN!! THIS STUFF IS MEAN AND EFFECTIVE !!
Worked for me. JUST BE EXTREMELY CAREFUL.

You'd have to be NUTS to use gasoline!! One small spark to set off the vapors and you're toast!