[ImperialCrown]

Is the PCM stuck on maximum advance? This may be internal to the PCM. No ignition timing marks, but the cam sprocket marks could be used with an advance timing light. Always diagnose first.
From the Wiki:

 

[ImperialCrown]

Not everything will or can set a fault code. That is why the troubleshooting procedure book has a 'no code' section.
Common causes are advanced timing, high combustion chamber pressures/temperatures and lean mixtures.

 

[ImperialCrown]

A tool with data recording that is graph-able later on a laptop is useful for diagnosis. Watch ignition advance and the upstream O2 sensor (or fuel injector pulsewidth) for mixture.
The knock (piezo-electric) sensor should also generate a voltage under detonation that (should) retard spark advance.

Instead of buying an expensive tool, consider paying a shop diagnostic fee (usually the minimum charge of 1 hr) or borrow one (unless you really want the capability for your tool inventory).

 

[ImperialCrown]

An EGR does lower the peak flame temperature (pressure) in the cylinder during combustion.
I would think an EGR malfunction would set a fault code, but they can be checked manually:

How to Test an EGR Valve: A Simple Procedure

Learn how to test an EGR valve in a few minutes to confirm you actually need a new replacement.

axleaddict.com

 

[ImperialCrown]

The black, plastic transducer comes with the valve. Make sure that you can pass air through the metal tube and head passages.
The bottom half of the transducer diaphragm was fed by exhaust gas to measure back-pressure and meter the amount of EGR accordingly.
The electric solenoid allowed EGR when the engine reached a certain temperature. You don't want or need EGR on a cold engine.