Back pressure question

[07graygt]

I just ordered two flowmaster outlaws 7". I'm gonna clap them on the ends of the h-pipe. I'm running jba long tubes with catted h-pipe. Am I going to lose to much back pressure not having the over axle pipes and regular mufflers? I've got all bolt ons including manifold throttle body and frpp cams. I'm also running 100 shot of nitrous through a plate system.