Well sweet spot and efficiency dont always coincide with whats still possible. For instance there were a few IXs when they first were released that ran a 36psi spike and made over 500 ft lbs. Lucas ran 34 when he made 515/500 ftlbs and the 506/472 was done at 31-32 as I recall.
I am running 30+ on E85 with stock rod bolts and head studs and 41k. I will admit that maybe I have a golden goose, but its done this for the last 36,000. I have revved it over 8500 a handful of times, free boosted the Green, free boosted the stocker, had a WG line burn through and peg on pumpgas (didnt realise what was going on for about 4 seconds until the knocklight went bezerk), and through all of it I havent stretched a head bolt or huffed a rod.
Maybe I am lucky, I would like to just think I am that good but I know better
