Performance drop off

[zx_volcane]

adding a few 10s of psi down the inlet isn't going to increase peak cylinder pressures significantly over what they are already, ie stupidly high.

Doesn't work like that, 10psi boost dosen't add 10psi to the peak cylinder pressure, its 10psi multiplied by the compression ratio (23:1) ish so you actually add about 250psi to the pre combustion peak pressure.

I understand this, but I'd expect peak cylinder pressures during combustion to be in the 1000s of psi

compared to running too much advance which will raise them significantly

or combining that air with enough fuel to burn it all which again would increase it significantly