I try to consume about 50 grams of carbs per day. With this eating routine my body does convert some of the protein (I use 50%) and I believe some of the fat (I use 10%) to an equivalent amount of carbs. With my eating style, I use the extended bolus for every meal. You will need to determine which meals in your diet need an extended bolus. The best answer for you can only be discovered through trial and error. The most likely meals to need this are the ones with a large % protein and fat, like 20%+ and 50%+ respectively.
Using your pre-pod I:C ratio of 1:10, a 33 gram carb breakfast needed 3.3 units of insulin to metabolize it well. Now that you've transitioned to pump therapy, you've found that one unit of bolus insulin is actually covering more carbs than MDI therapy did. Do I have that right?
Perhaps under MDI, your basal insulin was covering some of your meal or bolus needs. You now know that 2.1 units given for your 33 gram carb breakfast is a bit too much. Whether you need to use the pump's extended bolus feature would require some fingerstick readings out to about 5 hours.
I would test at hours 3, 4, and 5 to get an idea if any of the protein (or fat) is being converted to glucose in your case. If you BG rises at the 3, 4, and 5 hour marks then you can experiment with a small amount of insulin delivery extended over about 3 hours. Perhaps you could use 0.5 units per hour. The extended amount that you experiment with will need to make use of the 3, 4, and 5 hour data that you collect.
If I were faced with your situation, I would decrease the 2.1 unit bolus to about 1.8 and then measure your BGs at mealtime, 2, 3, 4, and 5 hours.
I sometimes eat a sausage and egg breakfast sandwich at Starbucks. It's served on an English muffin. I only eat one piece of the muffin; it contains 21 grams of carbs. The sandwich also contains 28 grams of fat and 19 grams of protein.
My breakfast I:C ratio is 1:4. I give myself 5.25 units of insulin to cover the carbs (21/4) and 4.8 units over 4 hours to metabolize the protein and the fat. That's an extended rate of 1.2 units/hour. I arrived at that extended bolus rate with personal experimentation. I started with a 1:4 I:C ratio but my experimentation led me to a lower rate, about 1:2.6.
I also know that my control is best when I walk for about 20-30 minutes at the one hour post-insulin mark.
Recording your results will leave to better analysis and decision-making. Once you have your breakfast sandwich meal dialed-in, you can move on to other meal challenges. I would encourage you to complete your basal tests for the rest of the day before you draw any conclusions regarding meal doses, extended and otherwise.