I need to replace the diverter valve - I unscrewed it from the hydraulic block but for the life of me I can't get it out. I even spoke to Viessmann tech and they advised twisting and yanking hard but this tosser is not budging AT ALL. The valve was replaced 2 months ago by someone else. Is there perhaps a vacuum of some sort, it does have two seal rings. God I hate integrated diverters.