So I've gone through my '89 vert and replaced nearly all of the engine sensors, EGR valve, 02 Sensor etc.
Car is running much better, but there's a very slight variance in the RPM's at idle (jumps between 675/725 constantly).
When driving to work today (50miles either way) the SES warning light came on. On the return journey home there was no sign of the SES light so I thought it was fixed.
I checked it this evening using TunerPro RT and my ALDL cable and its an error 32 for the EGR.
I have replaced the solenoid or the sensor on the manifold by the fuel regulator.
Whats the best way to diagnose this?

Also, see below a video of my readings at idle, are these normal? The car does smell like she's running a bit rich.
I also set the TPS value correctly using the guide, however I note its .59 when running and drops off to .57 when I turn off the ignition. I set it to be .55 when measuring the voltage between the pins on the new TPS sensor.

 

What is shown looks reasonable, but not much there due to the short running time initially in closed loop and then open loop after the restart. You need to let it run long enough in closed loop to allow some time for the BLM to stabilize in order to get an idea of the mixture error in any given cell. Let it idle for 5-10 minutes in closed loop, go for a 20-30 minute drive and record everything.

If data stops (which it will), need to key off for about ten seconds and restart to continue logging/recording again.

 

^^^What he said, need a longer datalog but what I saw in the short video prior to engine shutdown was your iac counts at 0. BLMs at 118 indicate rich. Also did you clean out all the carbon if any in the passages when you changed the egr valve?

 

You mentioned that you installed a new Oxygen sensor but that data showed it staying higher most of the time which it shouldn't be doing as it should average out closer to .45Vdc. That seemed odd to me... When Oxygen sensors fail they tend to go rich to prevent engine damage. When they fail your mileage will drop real fast and continued driving will kill the catalytic converter afterwards.

Was your Coolant Temperature accurate in the video? It was reading 224* at one point which is not a problem for the L98 but was curious. Defective CTS' happen more often than I would expect them to. They cause a lot of grief until they are replaced. Sometimes the wires are corroded where it plugs in. If you can take a temperature measurement from an Infrared thermometer to verify accuracy of gauge and data. If it read 100* ((f) sorry)) higher than reality then it would make the car have a hard time starting without any fuel enrichment. If low it would be like having a Choke left on in the old days and that burns more fuel.

One last item to check is the back pressure of the exhaust going into the catalytic converter. Converters get clogged up and fail often, then the cars runs Hot and Rich. To check you remove the oxygen sensor and see how much pressure you have try to escape. If a lot of exhaust comes out of the Oxygen sensor mounting hole then you might have a problem with a plugged or clogged Catalytic Converter. I pulled my original off and replaced it with a High Flow unit from Summit Racing along with new exhaust and it felt faster but Gtech said it gained almost 14 HP.

Must be a great place to enjoy a Corvette! I have never been to Ireland but look forward to someday!