I’m not quite sure what you mean by that…
turbo cars are all about flow…na cars usually require some back pressure.
On an NA car, bigger exhaust isn’t always better. On a turbo car, you need all the flow you can get.
There is a point where you will not benefit from a larger exhaust though. A t25 turboed civic will NOT benefit from a 4" exhaust over a 3".
yeah, that’s more of an turbo efficiency/size issue
Turbos have a stated max rpm. Going past that ruins bearings and seals. http://www.not2fast.com/turbo/glossary/turbo_glossary.shtml
you will not over spin a loaded turbo unless it is WAY too small for the application or you have huge boost leaks.
Why would the turbo over spin because you removed the exhaust???
it wouldnt
DING DING!!! Your right it wouldn’t. It may spool up a little quicker but it certainly wouldnt over spin JUST by removing the exhaust.
so lets hear how you feel on dual 38’s 
Twin scroll manifold??
My manifold is a twin scroll with a single 44. The way it should be and if I build a new manifold it will be with twin v band 38’s
ROFL at this thread
i have friends with 11 and 10 sec cars with reliable boost control with internal wastegates. Holset HE351 with the factory internal gate ported and another with a precision SC6152S with an internal gate. no problems.
Brian
I have no idea what size my wastegates are…nor do I care, haha.
internal gates have their places, and i feel pretty comfortable in saying that your friends must be running high boost or not revving very high, the internal wastegate holes are usually 20mm or less! I ran a T3/T4 with the internal gate on low boost with zero issues on my last setup (2 liter honda) with a stage 1 turbine wheel in a .63 T3 exhaust housing, and it was pretty quick spooling also. Ill have to post up again when i get the new setup running with the SC6152S and 38mm tial, but i dont expect any surprises, even at low boost
the guy with the holset has it attached to a 2.4L and revs to ~7k. anywhere from 15psi to 28. his is opened up as much as possible and ported so there is a very smooth entrance to the gate from the inlet of the turbine.
the other dude has it attached to a 2.5L 8V and only revs to 6-6.5k (4.09" stroke) and runs anywhere from 20-35psi. 10.66 @ 134 in a dodge omni lol.
im just saying that 44mm+ arent needed as much as one might think (ie agree with the thread intent) but on my next project ill be using a 38mm tial. hopefully in combination with a holset HE351 VGT.
each has its place. 
Brian
I think you should run one 60mm gate per runner and vent them out your hood.
Newman you’re a homo seriously. You didn’t even do awd. You don’t know shit.