I agree that IAT rising shows the air is highly compressed - but if the jack shaft is running inside spec then it's not necessarily inefficient - Vortech claim 20psi boost is achievable from the SC not many of us at that figure as far as I know.
Air gets hot when you compress it FACT, that's why we use intercoolers to keep inlet temps down, add hot air to a 10.5:1 compression ratio and you do bump into detonation as a side effect - the Twin Turbo builds are dropping to 8.5:1 pistons so they can run higher boost.
So to avoid detonation I went water injection I don't actually run meth (yet) and the difference as you rightly say is in the middle with water off I get detonation at 3000 rpm with it on no detonation so it's a solution to a problem. I also run 11.1:1 Pistons (cause I'm silly and was going high comp low boost)
What other options are their if he's not having a built engine? Although I agree he is probably better staying with the tune where is is on a stock engine - and he won't be happy even when he has figures in the 400's for torque
He could add NOS that will lower intake temps - may melt his engine though