the program used to diagnose the cat system is called "diagnozer".
on 2004-2006 models the screen is located underneath a dummy plate on the top of the injector holder body just over the fuel pressure sensor.
on 2007-2009 models the screen he speaks of is located inside the housing where the inlet tube is bolted to the injector holder body. It will be seated down inside with a small clip holding it in place.
K21/25 Tier 2 2004-2006 Injector Filter Part # 9042508330
K21/25 Tier 3 2007-2009 Injector Filter Part # 9196507800

how does the engine start? does it surge or backfire any while running? When you turn the key on , off, and back on can you hear the throttle body calibrate itself? If you replaced the vaporizer have you checked the fuel pressure and made sure it was set correctly? This system operated at 24 to 28 kpa fuel pressure so be sure it is set to that.

The fact that it will rev up the engine to full rpm's though leads me to believe that the fuel system may be ok. It sounds like your having a problem in the throttle body or accelerator. But the fact that it is not coding out is confusing. Generally when these trucks have any type of fuel system problem or accelerator or throttle problem they do code a DTC code.

One other problem i can think of is if this truck has the engine speed sensor reluctor wheel on the crank pulley with the mounted sensor i have seen this problem happen if that harness connecting to that sensor is damaged, the engine tends to not want to rev up correctly. You might want to check and see if this is on this truck.

Without a serial number i'm just throwing out educated guesses though ;o)