I have an Outfront EJ25 in my VMC Spyder. JDM engine. I got a new shorblock for 2 reasons. Engine number is on shortblock. I did not want a Japanese ID number on my shortblock since it is checked by DMV in some states. The other reason is to guarantee your cylinders are true so you don't get engine blow by. The cylinders need to be carefully inspected and the heads need to be rebuilt but a new shortblock is the key to engine longevity. My engine was built with high performance heads with performance in mind and has a "claimed" 230hp. It flies to 7000 rpms in any gear with a flick of the throttle. I have a Stinger ECU. I would say with the Stinger you need to let the engine warm up a while before you drive or it will stall. But after its warm it's bullit proof reliable. In my Spyder I went with Outfront because I wanted more than 175hp. I had the stock EJ25 in 2003 with the stock ECU in the first suby Spyder ever built by VMC. In no way did that car come close to matching the performance of my current Spyder. I wanted a stupid fast Spyder and that's what I got. So if your car needs to be stupid scary fast the stock EJ25 with the stock ECU will not be enough.
That said I have ordered a Beck 356 to be built in a few years by Carey and I will run the stock EJ25 with the stock ECU. This car will have AC, heat, stereo etc. I want the dependability of the stock ECU.