From the corvette forum, people paint their fuel rail covers a lot on vettes:

If you want the paint to stick you will need to rough up the part and use an Adhesion Promoter...

Scuff-it Paint Prep Gel - $13 (an old tooth brush helps here too)
Bulldog Adhesion Promoter - $14 - Quart Use as a starting spray mist and or add to primer/base/clear --- It is also a flex agent to allow some twisting on plastic parts without delaminating.

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