to me that you have to back like she did before, with external wastegate turbo seal the hot side and you have to make a flange to exhaust your manifull to place the external wastegate and boost their spirals define how you will have
as the wastegate will help to significantly reduce external is the turbo lag today. For me it is the surest way to maintain a stable boost without boost spikes.
And as the wastegate spring brings different psi there You can do the calculation as it is what you need, without ebc or bcm