Did a one-day DE @ Roebling Road on Sunday. Was excited to try Cobb Stg1 on the long front straight but experienced some stuttering at the top end of 3rd and 4th gear in the first two sessions. Had to revert back to stock for session 3 but was able to lay down my fastest lap ever at RR anyway! It was a bit cold, but had a great day anyway! Here's a video of my hotlap with data overlayed using Harry's GPS Laptimer.
I should note I don't have anything to augment the data collection. Just uses the iPhone GPS and accelerometers. I verified that the lap time is correct, but the instantaneous speeds may be slightly off. There are a few spots in the video where it is rather obvious.
Enjoy!