You may want to look at the article posted on planet-9 ref gutting standard cats, and the performance gain. Though the article is based on the 987 , the principle is the same on a 986. Personally I would buy a performance manifold without cats rather than gut the 986 standard units as the manifolds are so cheap. 987 manifolds are still very high priced , even for catless ones. If you gut standard cats you have the issue of a less than optimum gas flow , which will reduce power mid range. Lambda probe extenders may not work , but maxspeed offer ones with built in mini cats which appear to work very well.
987 Gen 1 - All Models Manifold / Header De Cat - Articles