In 2002 a friend of mine purchased a cutout from a competitor and showed me how it worked.
I thought it was pretty cool, so I designed my own, and installed two of tMachining Partshem Spring 2003 on my '79 Chevrolet Monte Carlo.
The difference is the opening for a 3-inch pipe can only achieve a 2 5/8 inch butterfly.
When you buy a cutout via the Internet, all that is taking place is bleed-off from the normal exhaust system.
Only about half of the exhaust air is blowing out the cutout, where the rest goes out the back.
I wanted to achieve full exhaust airflow out the side or out the rear. Plus with a cutout under the vehicle, it creates extreme vibration, if not piped out the
side of the car. My Monte Carlo actually ran worse when the side pipes were open and rear pipes closed, and vice versa.
I could only achieve good engine power when both rear and side pipes were half-open.