Power loss due to bad RR adjustment?

[gt93mustang]

I have not really thought about this much, but I have been seeing alot on RR adjustment and the difference it can make in the power a car can produce. I have FMS 1.6rr's that I installed myself (most likely incorrect) and I was wondering how much power is actually lost (or theoretically CAN be) from them being adjusted incorrectly. My car makes 290RWHP and 315RWTQ with the setup listed in my signature. I was really hoping to hit the elusive 300 N/A hp mark with my setup. Can I find another 10hp with a good rocker adjustment. By the way, the heads have been milled. Does this make rocker shims a necessity? Thanks in advance.

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MAC equal length headers, MAC Off-Road H-Pipe, Flowmaster mufflers, 373's, March ram-air kit, underdrive pulleys, 73mm MAF, 75mm TB, Saleen Intake (ported), Edelbrock 6037 heads (ported, polished, 3 angle valve-job 255CFM @.500), 1.6 FMS RR's, Wolverine 1087 Cam, 24lb injectors, MSD 6AL, Subframe connectors, Griggs Adustable Lower Control Arms, Lakewood 50/50 shocks, SSM Upper Control Arms... and probably some more in there I forgot