Post your dyno chart, and we will be able to be more helpful. Most people assume 15% for a 6-speed and probably closer to 17% for the auto. So if you have and auto and made 305rwhp then you would divide 305 by .83. This would be 367hp. My Black basic BPU Supra with an AFC made 406rwhp. It was a 6-speed so you would divide by .85. This would give it 478hp. It sounds to me like you have something wrong. You are getting knock retard at a minimum. Have you regaped your plugs, or are they stock?