Toyota Repair: High NOx, vacuum hoses, fault isolation

Question
QUESTION: I have a 94 NA MR2 (5SFE) that ran very high on the NOx.

I had the EGR Temp sensor disabled for the past year as it kept throwing a code even after swapping all components.

I recently put in yellow top injectors that flow less than the stock green tops because I am an idiot (5% less, not a big deal until WOT, correct?).

I have a HotShot header with a Catco cat (1 year old) out through a OEM Turbo exhaust.

I recently put Nology Hot Wires on the car (because they were cheap, not because I think they will make any power. My OEM ones were from the factory (135K)).

I can make the engine bog by applying vacuum to the EGR and all the other stuff associated with the EGR system has been swapped at some point in my fault isolation attempt (VSV, Vacuum Modulator, etc).

My readings are (reading/allowed):

HC CO NOx
15 MPH 79/125 0.03/0.50 3570/1636
25 MPH 105/136 0.20/0.73 4003/1591

I have no codes in the ECU currently. I ordered a new cat from Summit, but want to know if there is anything else that is showing? I think my AFR is probably good as the HC and CO aren't too far off the spec.

Update:

I reconnected the EGR Temp sensor and it threw code 71, as expected. I checked all the vacuum hoses and they are correct.

The code threw last night and cleared itself by this AM. It threw again about 1.5 hours into a trip, after one stop for food.

Even when the CEL is on, the EGR is getting vacuum from the VSV (in the parking lot, operating the throttle by hand).

Is there anything that rings a bell?  I can provide more info if needed.  As best I could, I checked the VSV and Vacuum Modulator per the BGB.  The VSV tested 100% and I cannot determine what "significant" force is for the Modulator when I do the blow test at 2500 RPM.  It seems to offer no resistance at 2500 RPM, just like it does when the car is off.

ANSWER: There are two things that can be done at this time, unless already tried replace the gas temp sensor or check for an open circuit between it and the ECU(time consuming) if the temp sensor has already been replaced then it's time to connect a scantool that can read the EGR gas temperature under actual driving conditions,there is only one thing that will turn the check engine light on and give the 71 code and that is that the computer does not see enough gas temperature at the egr valve. For whatever reason, it's the only way the code 71 will be triggered. The scantool should be connected and the temperature checked while driving or by activating the EGR system at about 2000 rpm, the temperature should read about 300 degrees +/-50. Let me know the outcome of this test and I'll get back to you.

---------- FOLLOW-UP ----------

QUESTION: Just to be clear, is the code 71 related to high NOx?  I was under the assumption that the EGR Temp Sensor only verified that the EGR was working and didn't affect the operation of the EGR circuit.  I had a paper clip in place of the EGR temp sensor for about 4 months and the code never showed.  I did swap the Temp Sensor, but it was with a used one.  

If the EGR is working, independent of the Temp Sensor working or not, shouldn't the NOx be lower?  Or does the Temp Sensor play an actual role in the operation of the EGR circuit?

I plan on taking it to the local Toyota dealer, but want to know if they are BSing me when they tell me the Temp Sensor needs replacing (at $134 plus labor)!

Thanks for your help on this!

Answer
Your'e correct the egr temp sensor has no control over the egr system, it just records the egr gas temperature and relays this to the ecm, if the temp is too low when it's supposed to be high such as under cruise conditions when the egr is supposed to be on it will store the 71 code, when you short it out like you did it will see this as a high temp reading and the light will not come on. This is the reason for the code. I think there may be another problem causing the high NOX readings during the emission control test,high nox emissions are due to higher than normal combustion chamber temperatures, this is why egr systems were introduced many years ago, it's sole purpose was to reduce combustion temperatures by reintroducing exhaust gas back into the combustion chamber, this has a cooling effect which reduced nox emissions, higher emissions can be caused by higher compression than normal due to carbon builtup on the pistons or inside the combustion chamber or an engine that runs hotter than normal or timing that's too far andvanced, you can actually have higher than normal nox emissions without turning the check engine light on but since the light is on and there is a 71 code I gave you an explanation for why the light is on, to answer your question, no, the code 71 is not related to high nox readings so even if the replacement of the sensor fixes the code 71 I think you still have a problem that is causing the high readings, I apologize, I guess I should have been more clear in my first reply.