My suggestion to you to to treat those areas like the other PAINTED surfaces of the car, however not to aggressive. No compounds. No glazes. Just clean them well and protect them with a good quality HARD wax. Not a liquid wax. Also be leary of areas like that painted trim strip around the front grille. (I'm referring to the grille itself.) Don't get wax/sealant on the non-painted plastic. It is very hard to remove wax from these non-painted/texured surfaces.
I've had great success with some of the products from Ardex Labratories. If you have a Black GTI they make a machine polish called '4212 Seal-B'. Tremendous product. A little hard to work with, but well worth the effort. In your case, a Red GTI, there is a product called '4209 Flint Glaze Wax'. This works very well on bright colors (Red, Yellow, Blue, Bright Green, and Pewter/Silver). Check em' out.
(http://www.ardexlabs.com/index2.html)
I've had great success with some of the products from Ardex Labratories. If you have a Black GTI they make a machine polish called '4212 Seal-B'. Tremendous product. A little hard to work with, but well worth the effort. In your case, a Red GTI, there is a product called '4209 Flint Glaze Wax'. This works very well on bright colors (Red, Yellow, Blue, Bright Green, and Pewter/Silver). Check em' out.
(http://www.ardexlabs.com/index2.html)