Most of these operators tend to baby the engines. The original 115 and 130 fuels aren't available now. Racers use additional TEL (tetraethyl lead) in their fuel to help control detonation and lube valves. The P40 in particular, without an intercooler, had an issue with detonation at high manifold pressure settings (up through the E model, with the single-stage blower). Consequently, use of lower power settings is common.
Water injection or anti-detonation fluid injection (ADI) is also an option, but again, most operators respect the engines by backing off on the power. The P40 uses three coolers because it doesn't take much of a coolant loss to lead to an overheat on the engine.
The other side of the coin with 100LL is that one hundred low lead is actually fairly high in lead, and lends to fouled spark plugs, rough engines, and preignition, detonations ugly step sister.
There's not a lot of option when it comes to available fuels; the engines are run on 100LL.
Allison agreed to an increase in emergency use of 60 inches manifold pressure (full military was 48 for the E), based on reports that pilot shad been pushing well above that, but also indicated that the aircraft should be pared back and limited to a value less than 60 at max manifold pressure settings in the earlier P40's. Allison powerplants were in production then, and better suited fuels available, too. Allison's comment in their memo on the subject, dated 1942, should be noted:
"While we cannot help but feel pleased that our engines are standing up apparently to the particular squadron's satisfaction under these conditions, we also cannot help but feel that the selection of such high manifold pressures may be based on inadequate testing and that they are apt to result in occasional failures which may occur some time after the operation at such high horsepowers but when operating normally or even cruising with resultant loss of pilot and aircraft."
Also notable, in the same memo, though not really a revelation:
"Our tests indicate that under detonating conditions a hole can be burned in a piston which may result in seizing in the cylinder and breaking of a connecting rod in a matter of thirty seconds from the time the detonation starts."
https://web.archive.org/web/20160228...39%20abuse.pdf