SuperSprint headers with RPI GT combo?

[M6_kelleners]

Hey everyone, I really need your opinion on this one and who else do I have to discuss such matters with except you guys . I'm starting to feel that my kelleners-sport exhaust set up is out dated compared to the fully developed catback systems offered by RPI today. Kelleners-S replaced my secondary cats with 200cell high flow HJS race cats, retained my stock X-pipe and finally used there Kelleners-S rear mufflers which turned out to be an eisenmann sport muffler with a kelleners-S logo as I found out with time. I think the only component of the exhaust they used which made all the difference is the Supersprint headers since my car proved to be much faster than a stock M6. So knowing that I don't have the most efficient exhaust setup, I really want to get the full RPI GT system, but I have no clue what will the outcome be when combined with the SS headers since no one on this board ran this setup before. Does anyone know what sort of HP figures is expected when combing the RPI GT setup with SS headers? Could it be possible that I could face a problem of back pressure when used together? I have no doubts that the RPI system on its own proved solid gains and probably the lightest exhaust out there, but I haven't heard of anyone running with the RPI & SS combo. Any feedback is highly appreciated, thanks.