having recently purchased a z, it is fitted with a cobra front bumper which was blended into front wings, its has cracked and separated. What can i use to stop this happening in future, im thinking some flexible filler.

Any ideas anyone?

Flexible filler, or fibre glass done the right way can work, or just don't do it, if the bumper doesn't quite meet right, and that's why the blending, just fill, then slice a seam where the bumper and the wing meet, that will make them line up pretty much perfectly, without the hassle of it cracking again.