Sounds like a great ride and agree with most all points. BUT, your Viper has no throttle response?? Better take it in and get it checked. I have had 7 and pretty darn good response. My 2010 Coupe with the new 5th gear is quite a ride.
On exhausts I have both the Heffner and Henessey and like both--maybe, just maybe the Heffner tad better but that is only my opinion. They are both great and MUCH better than stock.