Splice in to the original wiring to the angel eyes.

Install an "ignition on" power feed to the angel eye wiring. Put in a blocking diode so no power can travel back up the original wiring.

Done.

Whenever the ignition is on, the angel eyes will be on. No power will travel back up the original wiring, so the vehicle won't "know" they are on.

Turning them on via normal switching won't affect a thing.

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Cheers,

Anthony