youll be surprise what decent induction can do. As a general rule, the exhaust can only gain power when it becomes one of the limiting factors. So until you over load the exhaust, it will be more than fine.
The magnex wont casue you to loose power. and back pressure is very misundrstood by most people. Its not where the gasses meet atmospheric pressure, but how the pressure changes inside the haxhast system. So, if you had a 2" system, then added a 2.5" section, where they meet, the back pressure would be reduced. And fitting a back box could do this, if its much marger than teh standard system. However, lower back pressure would only lose power on an engine without VVT where they cant change the amount of valve overlap whilst the engine is running. So at low rpm, where valve overlap occured, the exhaust valve would actually stay partially open during the intake stroke. The reason for this is at high rpm, when exhaust gasses are expelled and pushed out, they creaste an area of lower or nagative pressure behind teh echaust valve. This would help the engine "suck" in more combustion mixture at high rpms cause of the lower pressure zone, just in the begining of the exhaust manifold.
but at low rpm, becasue there is more time for the mixture to enter the cylinder, some unburnt mixture would therefore actually excape through the exhaust valve......and VE would be lowere than nesissary. Basically, lots of valve overlap is for high end power, little for low end torque. back pressure can be used in the same way. Little back pressure for max power, the right amount for torque.
