This looks wrong to me

[Anonymous]

Does the engine rev freely in neutral?  or is this lack of power only while driving?
Does your CEL (MIL) illuminate?  You will need to run the engine two times once warm to set most of the codes.
To test the Lambda Sensors, Catalyst and Fuel Purge system you will need to drive the vehicle twice covering high speeds and low speeds for 10 miles each (None of which will affect power).

A few items to look at:
Fuel system - Engine is running so the pump is working however low fuel rail pressure could affect the amount of fuel at high load.  You will need a fuel pressure tester to check this.

Intake system - You have checked the air filter but what about the rest of the system?  Also check the Throttle.  Does the butterfly valve open fully when the accelerator is pressed?

Exhaust system - Broken pre-catalysts get stuck in downstream cat or back box.  This can have a dramatic effect on the power output.

Ignition System – Only really causes problems at idle.

All of the engine sensors should be covered by diagnostics and illuminate the CEL (MIL) however the 'Throttle Position Sensor' can sometimes be faulty but still in range.  Try measuring the voltage from this sensor.  There is normally a 5v supply on these sensors so you can measure the output something like 0.2v – 4.8v from Closed to WOT (wide open throttle).  This sensor can affect fuelling on acceleration but the engine 'should' still run without it.

[Anonymous]

The odd thing about this is that although I have swapped my Main Cat for a JDM after the pre cats fell apart I have had only one CEL which went away on the next engine start. I would have thought that I would have a constant CEL as the aft Cat O2 sensor is missing and I have covered more than 10 miles as suggested.

I will swap the rubber injector seal and check the intake over again tomorrow and if that isn't it MR T can fix it - I have had enough of laying on cold driveways  s:( s:(

Thanks for the hints though James