I guess using the dyno they use, it would be hard to have an disappointed customers... Then again... With E-tunes, if the person doing the pulls isn't on a perfect road ( level, straight, no wind etc ), then someone could be falsely disappointed, or falsely happy.
Like the latest car that put down like 238whp in puerto-rico on a stock turbo in 90+ degree 100% humidity, all dyno's should be taken with a grain of salt. Its a tuning tool, not a measuring stick ( 12 inches is the same on EVERY ruler ).
Trap speeds never lie (assuming you get reasonable traction ).