First of all, Toyota typically designs phenomenal combustion chambers that allow one to run the leaner, more timing advance, andif necessary hotter charge air temps (from running more boost for given intercooler) than most designs while maintaining stable combustion.
Before you look at EGTs, first get your car wideband lambda monitored, your factory nonlinear O2s do not provide good resolution in WOT enrichment (which is why the computer does not even use nonlinear O2s for fuel trim in WOT enrichment mode).
Convert your O2 readings to the A/F ratios. General guideline 10.5:1 to 11.5:1 air fuel ratios if you want OEM-safe tuning: that means no pinging (assuming all other systems are in working order) all the way up to top speed. If your EGTs are going past 1700 deg. F, then lower boost because your knock retard is causing the combustion too occur to late and you could thermally fatigue your exhaust valves to eventual destruction (seen in 2 MKIV JZ motors and one 300ZX TT motor and I'm sure one of the few failure modes in many other forced induction motors). You can back off timing by a PCM reprogram based on the notion that it takes less timing retard to prevent knock that timing retard to stop it. If you refuse to lower boost and also wish to prevent excessively high EGTs then run more octane which will allow you to run more octane.
There are also instances when everything is in working order, boost is at a reasonable level and the motor still pings; cases seen when someone is trying to run very restrictive exhaust...(e.g.: my friend's '94 TT AOD-rebuilt Supra with the stock cats would ping during firm automatic upshifts with a bit of work done to it). My Trans Am was at its edge of detonation on pump 93 when trying to make 579 rwhorsepower through dual 2.5" random tech convertors despite 8.5:1 CR and a sane 11psi intercooled boost.
Finally my rough guidelines (there are many other variables that enter into the precise tuning A/F) for other driving conditions (if you still have high EGTs, run less boost or more octane):
10.5:1-11.5:1 A/F: pump 93, standstart to top-end driving, road race
11.5:1-12.5:1 A/F: race fuel top-end driving or pump 93 hot street driving up to and a bit beyond the quarter-mile, road race with race-gas.
12.5:1-13.5:1 A/F: race fuel top-end driving with exotic exhaust valve materials, ceramic coating the valves, strong ignition system to prevent breakup, tons of power made on lower-boost pump gas setups if you intend on saving the turbos in wear/tear and race only up to quarter-mile, but make sure to have a really free-flowing exhaust (4").
with 1.2 bar boost in a 4th gear pull. Though i'm pretty sure it's fine but still thought to ask u all !
