Are you interested in the dyno readings on the HP and torque or the accuracy of the O2 readings from each pipe?
I allowed a dyno operator to install 8 O2 bungs in my race car headers to dyno a B 1 motor I built for a customer several years ago, that motor had a cast single plane dominator flange manifold, not much carb. tuning was done on that test
On your deal I would install them and tune the motor and then remove them to see if the probes sticking into the headers affected the readings or not