@ 750mg /week, your test should be at very least 2500 ng/dl if it's a true 750mg. It could be as high as 4000 at that dose. It's a ratio, so the higer the dose, the ratio should increase more comparite to that dose.
For example (these are NOT any true chart numbers, it's just demonstrating a ratio increase vs a dose increase):
100mg = 300-400ng/dl
200mg = 650-900
400mg = 1500-2000
800mg = 3200-4400
and so on
I've seen guys #'s with HG gear @ 500mg/week have over 2000 ng/dl.
200mg/week HRT should put you at about 650-900, depending on your ht/weight. which is a high normal.
Are you using HG stuff?
1600ng/dl for 750mg is shit bro, when it comes down to it.