My experience is the same as Big Pistons. My EGT's settle down in flight, though there are some power settings better than others at evening them out.
As for the induction cross tube on 470/520/550 engines, they are there to tune the induction volume. As you have not recently changed it for the wrong one, it could only be a leak which would introduce a change. However, if the induction has been apart and carelessly reassembled, with the wrong part, the mixture distribution will be horrible. There are three different sizes, and when we changed a 520 from being injected to carburetted, it required a lot of experimentation with each of the three sizes to get it running properly again.
In the mean time, don't worry about uneven EGT's, remember when we had no EGT, and didn't know to care?