Time in grade is one of the things I left in the service... ... . It has it's place, but is not always correct.
jkern, your result is the polar opposite of what i have personally seen and what has been reported by others on this board. Not sure what the reason would be.
Back to the topic, peak power will be affected very little with or without the elbow. EGT will be affected. WITH the elbow even towing you will have one heck of a time hitting 1100 pre, WITHOUT you will be able to hit 1300 fairly quickly. It would not bother me to run the EZ without the elbow at all, unless towing. If you tow you need the elbow, or you will have to drive by the pyrometer. Empty it really won't matter. Add some injectors and this will change.