I still stand by my definition when it comes to the pulse/response tests. The 2hr OGTT is only covering the stage-1 response. A 4hr timespan would start to show part of the basal response but is still insufficient in that respect. It would require monitoring and recording of at least 6 hours to get an idea of the overall IR response. I believe HOMA is similar in its coverage too, it being based on a step change from fasting and limited time recording.
As regards the effect of diet, the Stage-1 response is triggered by amylase, which is in turn triggered by any carbs entering the mouth. It is in the saliva response to dietary carbs. This is a fixed trigger and is not dependent on carb load except in respect of eating and chewing time. But amylase has two stages. the first is as above, the second is the one that occurs in the gut when carbs are detected in the digested food within the gut, and this controls the basal response. This second stage is carb load dependant. There are other enzymes such as lactase, protease, lipase etc that come into play at this stage. This amylase is also GI dependant to a certain extent. It is also food transit time dependant since it occurs mainly in the upper bowel tract, There is a further stage that occurs in the lower bowel that happens as fibre is digested. This last stage is fermentation that produces sugar products to feed the gut fora and enzymes and does not really enter the bloodstream.
Some artificial sweeteners have been shown to trigger an insulin response, and this can lead to raised insulin levels since there are few accompanying carbs to work on. It does not seem to trigger the second stage of amylase and basal insulin since there are no carbs going into the gut. Thus the basal response does not follow.
Since it seems to be the stage 1 response that goes walkabout in T2D, then the OGTT will be mainly showing the start of Stage 2 basal response. It will certainly show if the stage 1 is compromised, or held back by mitrochondrial IR. It will also show if pancreatic insufficiency is present or inhibited by adipose IR but would probably not be suitable for a quantitative evaluation.