After the vibration appeared, he contacted Blueprint who gave him a series of procedures to eliminate possibilities before pulling the engine out and sending it back.
During the diagnosing phase, the engine was still in the car and disconnected from the transmission.
First off, sorry to hear that you are having issues with your engine swap.
What it sounds like to me is that something happened when the car was on the dyno.
I am a little confused, so I hope you can help me understand this a little better. Once the mechanic started in on the diagnostics of the vibration, they at some point removed the transmission? Is that included in the $1,500?
I agree with you that they could have, a probably should have, changed the flex plate at that time, especially if they are going as far as to charge you for the test harmonic balancer. But coulda/shoulda/woulda ...
A couple of questions: Maybe I missed them, but ...
Why have they not sent the bad flex plate back yet?
Why have you not heard back from Blueprint on how the engine dyno test went with a known good flex plate?
Why is Blueprint having to keep the engine another couple of weeks before sending it back if it was JUST a bad flex plate? Won't that make over a month that they will have had it?
I am betting that Blueprint is going to come back and tell you that there was a bad bearing and they are going to blame the 2.5 oz difference on the flex plate and that it is not a warranty issue.
Anyhow, I wish you the best of luck in getting your car back up and running.