yes id like to know if they do make more gains than ams

 

That isn't really the case. Turbo cars are not like N/A cars in which more backpressure will create low-end torque and free flowing exhaust will cause nice peak horsepower numbers but kill your peak torque.

For turbo cars, it's more like you break over a threshold in the level of restriction where you have not enough restriction and the turbo's output pressure will creep up and down as it fills / tries to fill the void. You want some restriction in your exhaust, but the main need is at the turbine outlet only. With no restriction at all, losses are made because of boundary layer separation cause by a transition in pipe diameter (hotside outlet to O2 housing) at the point where turbulence is the most affected.

In other words, if you dump straight out of your hotside into open space, it will cause spikes and boost creep. If you step down your exhaust into an O2 housing and then into some form of a downpipe, it will "smooth out" the exhaust and cause it to actually flow more efficiently. Think of a venturi tube.

Super large exhaust pipes are nothing more than overkills and usually just cause clearance issues or noise polution tickets.

If you're really looking for the best flowing exhaust, get a 3 inch with an external wastgate that dumps to atmosphere.

 

Hpf!!