Yeah good idea a comp test should show this. If you have a slightly bent or miss fitting valve this could cause these symptoms. Even if you used all new valves, if you have not set up the timing correctly you may very well have caused a collision between one of your valves and pistons so bending it. Also this could be an explanation for tapping under load. The valve could be colliding with a piston when open.
Did you do rebuild the head yourself or have a company do the rebuild?