Hopefully this image loads. This is a graph of just two shots (500 mgs)per week of sust for 15 weeks.
The second image is just one shot of 400 mgs of test deconate, which is what you did on your last shot. And that is just the deconate ester without prior build up.
Since you were using sust for a while your levels will be higher.
The day count is at the bottom of the graph and obviously the mgs is on the side.
Look at the first image, see how the test level is constantly bouncing? Your body is not at equilibrium. Up down up down.
Now one week or so past your last shot your levels have come down. But they are more consistent. They are just slowly dropping. You are still well above natural levels.
I think (I experience this myself) that since your levels are finally not fluctuating your body can finally adjust properly and handle the amount of test it has, thus the higher libido. We don’t think of our hormone levels as stressful to our bodies but they are. Your body can finally feel steady and safe and not constantly reacting to a different level. I am willing to bet the hormone levels triggers the fight or flight response in some degree. Your body is no longer “worried.” That in combination with a level of test that is still well above natural level allows the higher libido. Natural levels are something like 7-10 mgs a day or around that.
Just look at the fluctuation two shots of sust did. It’s like a 40mg fluctuation after just one cc shot. Imagine the fluctuation if you were taking a two cc shot. That fluctuating has to work against your body feeling safe enough to fully capitalize on the libido potential of that amount of test.
That’s my take but I think Iron had a good point too. You might just finally be in your “sweet spot.”
I have noticed the spike in libido myself at the end of a cycle. I have noticed so much that I am currently sourcing test undeconate because 200 mgs a week in two equal shots puts the active levels between 15-17 mgs per day once it levels out and I think that would be the perfect cruise dose for me and there is so little fluctuating.