balanced flex plate on balanced 360 cid

I have installed a b&m flex plate on my blue printed and balanced 360.
When i idle and rev her up I have a vibration through steering wheel.
The car cam was set up for circle track so it is heavy the harmonic is a balanced one.Is it possible that the flex plate is not working with the rest of the balanced combo? Just hate to crack everything open if I don't have to but it is begining to look that way .
Any input would be great. Car has not been on the road and I have only done a small burn out to make sure the transmission rebuild went well
There didn't seem to be any vibration during the burn out ????