I have a question regarding this. The plates are for just attaching a PI manifold to the current '96-'98 4.6 motors without changing heads for approx 20-35 HP gains. For those of you that have done PI mods (Both Intake and Intake/Heads), what is the average cost for these mods and what are your experiences in the changes in the mods. I also noticed that the head raise the compression to 10:1 so I am sure higher octane gas would be required, so what would minimum octane be to run the full setup? Appreciate any posts regarding these mods.