You need to check the installation instructions and clearance specifications for the exact range you are installing. What people don't realize is that sheetrock and tile over a wood framed wall is NOT considered any more fireproof than beadboard. You can still burn things through a pan or a clay crock, and the flammable material behind tile can still get extremely dry and ignite. According to the International Residential Code, you would need a 1" air gap between the tile and Sheetrock with open edges to let the heat out in order for the tile to count for any reduction in clearance to the combustible wall behind it. Most high powered gas ranges have an "optional" back shield that really is not optional, but required in most cases. Some ranges have a zero back clearance UL listing.