I just installed and tuned my car at specialtyZ, 3" super-splits downpipes and 3" testpipes to 2.5" . I can't really explain how it feels other than its so much faster as spooling and being able to use the extra 80 to 100lbs of torque i gained. I will try to get the dyno graphs and you will see my gains with the 3" super splits DP. They are worth the extra money.
I have the 530BB turbos.. i thought it was fast before. i can't believe how responsive my turbos are now. BIG Different.. Hope this helps.