Does anyone know how low/high the back pressure should be. I had a custom catback made with a reactive tunable bomb muffler. Its almost straight pipe. Will that effect the preformance of the engine. If so any suggestions on how to fix it.

Thanks

 

For optimum power output, you should keep the backpressure as low as possible. However, excessively large exhaust pipe will slow down the exhaust velocity and kill torque. What you want with a small N/A engine is small(ish) pipe and low backpressure.