That really sucks man, nothings more aggravating than trying to do a perfect job and it turns out bad, i hope it's not as bad as you think it is, any chance the vibrations above 2500 rpm might be caused by polyurethane engine mounts/ tranny mounts if your running them.
I'm not sure what engine management your running, but this is just an idea.
If you are running the megasquirt, maby somthing is out of wack with timing/spark, wont notice to much at idle but then when rpm increases things get crazy, maby just hook up the motronic, if it's not already hooked up.
For the brief moment that you did drive it, It's good to hear how effortless it was driving around,

Failure is not an option
Keep pushing forward.