Over rated, extra work, to gain what? A few hundreths? A tenth? We bracket race anyhow. Want to go faster with less effort? Take the passenger seat out and the back seat. Takes 5 min tops and will yield you a tenth or so. Run cutouts or just make it run well through the pipes. The fact that you think it will run better after dropping the exhaust says that it's 1. too fat 2. too small of a diameter 3. not a high flow muffler and 4. the car is too heavy.
