Peak hp. I didn't say you were jealous...I said "some". The springs don't literally have anything to do with how much they flow. Valve sizing is more of a factor. Yep they flow about the same, but not the same. The PI heads (port holes) win. The headswap is pretty cheap...get PI heads/cam for $350 a head. That is cheap. A lot better than the $1550 bucks I spent on my heads. A tune would be a better option. I'm sure the ECU's are calibrated differently considering they have different flow in air and timing of the cams.