The Dynomax Super Turbos are great if you don't like power. They sound good, fairly quiet compared to some other mufflers, but they are very restrictive.
How about a side by side test?
I also have Doug's electric cut-outs. Have had them for 20 years on both the big wedge and this big Hemi. We have a cool 1/8th mile strip 5 minutes from me that I used to hit regularly. Especially when they had the KOS series going. My car was 2 time class champion. So, I have ran it many times through the full exhaust and with the cut-outs open.
Why don't you guess the actual difference in ETs?