I have installed the flowmaster series 50 after the cat dual exhaust, behind the rear wheels.It has a nice drone to it.....it has a tuff sound at idle and a deep gutsy sound at driving speed.As for the k&n filter the drop in is a waste of money...there are no advantages as far as performance.Your better off keeping your oem (toyota) filter in for exceptional filtration.There was a thread on the filters i think at the top of this site.As for the gains of horsepower or perf with the k&n intake system it's minimal from what the thing costs and what you accually get out of the engine.