I have the tubi exhaust installed a while ago and i can't feel any gain out of it, but after I installed the V-flow, I noticed a gain in power. The sound of the exhaust also changed to a more aggressive and throaty sound. I LOVE IT!!! I cannot help myself from not speeding because the car just sounds awesome at high rev. I can hear the car BREATH better. I asked the tech at porsche why would the V-Flow allow me to feel more power and he said that the TUBI exhaust that i put on earlier is probably not working in its full potential because exhaust is for shooting out air and that the TUBI exhaust allow the car to shoot even more air out, but at the same time, the car is not sucking in enough air before i install the V-Flow to accommodate the exhaust. He said that I am feeling the difference because my car now is able to suck in more air and at the same time shoot more air out. I don't know if i am making any sense but the main point is that V-Flow ROCKS!!!! I highly recommand it!