Part throttle cruise is fine, decent idle, wires are only a year old (which may not mean much I know), but when you mash the throttle it falls flat on its face. Sometimes you can feel the timing being pulled too / borderline detonation maybe. Trying to decide if I should start with the Cat-canvertor, or the fuel system. Suggestions?

defintally check the cat converter..give it a few kicks if it rattles bad have it replaced at a good exhaust shop..have a high performance one put on there..my old 93 SSEi did the same thing almost like a dead miss at WOT..the HP cat converter is a nice set up..much smaller than the huge factory one.
You might consider scanning it for codes...if u have a bad CAT it could also cause premature death of your O2 sensor.
Other ideas:
Throttle Position Sensor
Most Likely: Cat Converter