I think we all know the importance of testosterone, I think that the androgen receptor is overlooked. I remember seeing a study showing a correlation between squat 1rm and androgen receptor concentration. I also read that taking a carb/protein drink after and before a workout prevents the downregulation of the androgen receptor after a workout. Is there anyway to increase androgen receptor sensitivity/concentration?
ReceptorMax is suppossed to help with this. Have you ever checked into it?
"Heavier" training in general, along with shortened rest periods, has also been shown to increase the body's production of testosterone.
From my own experience, performing 3-4 big lifts (Squat, Dips, Deads, and Pull Ups is one example) in a circuit like fashion, resting just enough to maintain my performance in each lift, keeps my intensity and focus at a high level for the duration of the workout. I typically do as many sets of each as I can, aiming to add weight each set.
Once I can't add weight and get all the reps (I usually do between 3-5 reps for each exercise) with good form, the circuit/workout is done. Start with a weight you can perform with maximum acceleration and work your way up from there.
The key is to "quit while you're ahead". Continuing to grind out rep after rep or set after set, will have an adverse effect on your T levels.
Hopefully this helps.