I'll try to lay this all out so everyone can easily understand this or so I hope. I by NO meas want to make this a this versus that, etc...
I've played with timing tweaks or tried t on the new VHR engines for the last couple of years with no real benefit on an NA car. I was thrown under the bus somewhat in doing the testing for both the OP and Motordyne. I did a true comparison back to back originally when Tony @ Motordyne was at my shop. My job was simple, dyno on the OP's Invidia catback, install the Motordyne E370 catback, dyno the new catback and at the end unrelated to any of the exhaust tweak the tune for the changes the OP made in his mods.
Tony offered the OP a tune at Church as a consolation to the OP's unfavorable review of the exhaust. I personally have nothing to hide from as I have played extensively with the ignition maps and have done lots of talking with Jared @ Uprev about timing tweaks on the VHR. Jared and I spoke today via e-mail unrelated to this situation about knock maps on certain ROMs that have no High Det maps. Jared's response from today: "The newer ECUs do closed loop knock control somewhat differently. They don't use the "high det" map anymore, they just continue to pul timing as long as there is still knock so there's no switchover. The ECU will pull a LOT of timing. They will also advance the timing quite a bit on their own, which is why we're finding it so difficult to make good power gains on these newer Nissans."
How the dyno runs are performed can have an affect on power between runs. Letting the car cool down for longer periods of time, airflow, what gear the run is performed, etc... can all have an effect on the end result.
When I performed the testing on the exhaust systems and lastly the tune differences I did it in the exact same manner allowing for the same time to cool for each run, etc...
At the end of 3 pulls on the Church tune we reflashed to my tune. Here are the results of the runs and the differences in Air\Fuel using my equipment. Again, there are no smoke and mirrors on anything I did. I told the OP when I was reflashing after the 3 pulls we made and brought the laptop into the car at that point.
I will show all the pulls made and differences in AFR. I will also plot the runs in "speed" to show all pulls were made in the same gear as to not affect power. I like to run the mixture leaner at lower engine speeds to help bring up the low end torque. Blue runs were on the Church tune and the red runs are my tune. This was all done on the same day within an hour. The reason I feel that the first two Church tunes were lower across the powerband is because the timing was advanced to far and the ECU was pulling timing and by the 3rd run the ECU adapted to run its optimal timing. This is based upon what Uprev has said and my R&D the last several years.
Run 1
Run 2
Run 3
Run 3 of Church vs a 4th Pull on the SZ Tune to confirm.
I really hope to lay this all to rest and move on. For anyone looking to buy an exhaust the Motordyne is a nice quality piece. Tony put out a great looking system.