Correct, there is a lot of conjecture around this subject and exhaust tuning in general. A common belief which is key to this subject is that some back pressure is a good thing and is required to make good low to mid-range torque, this is a fallacy. Think of the engine as an air pump, the more air it can move the more potential power it can make. So, an increase in pressure which is opposing the direction of flow will never be good for engine performance.
As the engine has been designed and the ecu calibration optimized for the supplied exhaust system, we’d always recommend customers don’t run with a noise trap if possible. If you must use a noise trap expect a 5-15whp reduction in peak power depending on the type of noise trap used. The air fuel mixture will also richen due to a reduction in volumetric efficiency and the EGTs will increase. However, providing the noise trap isn’t overly restrictive, you’re using a good quality 98ron fuel and keep the engine temperatures within the recommended range, you should be fine.
We’d always recommend using Radical’s range of quiet silencers before considering an additional noise trap, as these have been designed to attenuate sound without significantly increasing back pressure. If you were to require further noise reduction then the Decibel Devils kit is our preferred choice, but make sure you use lockwire as an additional safety device to prevent it from coming loose.