Quote:
Originally Posted by Wheelhop
Wrong. 
Backpressure is always bad, period. |
+1
This backpressure myth won't die.
Backpressure negatively effects Volumetric Efficiency, as it is a restriction. Higher VE means better fuel economy, power, and torque.
Open headers can be a great idea, but just unbolting the y-pipe isn't the best way, IMO.
Ideally you make up some turnouts to route the exhaust gas away from the cabin of the car. I've used cone inserts before with success, to keep the noise more reasonable, similar to these:
Dynatech Vortex Insert Cones - JEGS