The same as twice as much test 200.

I ran half a ml of this stuff every 2 day's,so 600-800mg's a week.Dropped onto 500mg's a week of cidotestone test enthate,and the cido is kicking my arse harder than this ever did.But 400 is a ed or eod sted

Are you happy at your current level ??

test400 has:

Test E : 150 mgm/ml
Test C : 150 mgm.ml
Test P : 100 mgm/ml

You won't notice a lot of difference between E & C,
but 100 mgm of P on top of your regular Test will give a 1-2 day bump.

C & E have a half life of 5-7 days
P has a half life of 1 maybe 1 - 1/2 days.

You'll probably notice a difference, 500mg / week is not overly high, but becareful.