Re Labour costs. Any of our GXP kits can be installed in less than 1 hour by a qualified garage. They really should only take about 1/2 hour. The converter on the other hand would take 1 to 2 hours. It's much more difficult. The engine has to be raised just to get the stock cat out. As for warranty you can do anything from the cat back without any warranty issues. When you change the cat is when it gets into muddy waters. Its always best to check with your dealer.