3 inch will be a benefit even with stock turbos. Also Dual pops work on stock turbos as well. The reason that dual pops work better on a stock turbo is because of the restrictive stock Tee. Basically because the two sides pull from each other they cause a significant restriction. We find that on stock turbos the dual pops offer about 20 hp. The reason the down pipe is so important is because the turbo works on a pressure and temperature differential. You want as much heat before the turbo as possible and you also want pressure before the turbo and no pressure after the turbo. Turbulence is a huge problem and is why the old open 3 inch down pipes that were on the market years ago did not work well and threw us off. This is also why separating the wastegate works better because of less turbulence right after coming out of the turbine. The split design increases the exhaust velocity. With the recent testing of 3 inch and slowly growing it to 3 inch from the time it leaves the turbo, We have found that we can get down to zero backpressure in the exhaust. The current down pipes have 6 psi back pressure. By slowly growing the turbine pipe it helps pull the exhaust out of the turbo and allows more of a laminar flow. From the testing we have been doing we have found the greatest gains come from and are mostly in the down pipe/test pipe area. Going full 3 inch does offer some gain, but it is less drastic and the gains from the cat-back being larger are mostly in the high RPM Range. In contrast the proper down pipe and test pipe offer huge gains from off idle all the way to red line.
