Can I run the twin turbos wide open without any throttles, then through 2 water IC's to a MAF then a throttle and normal sc setup? I was thinking I would need a blowoff vavle somewhere so that when the throttle snaps shut the boost will have somewhere to go, or maybe one the opens on a certain vac # and at high boost limits as well?
yes this set up is relatively easy to do. the turbo you use will dictate the airflow you will have. the turbine housings for your turbos WILL have to have internal wastegates. when you look at the turbine outlet it'll have some sort of flappy valve and a rod connecting to a pressured bypass valve from the compressor. not the cheap ones you see for 200 bucks.
first you need to find your airflow by using this formula;
horsepower(hp)Xair fuel ratio(afr)X (BSFC.55for turbos /60 reducing hours to min)
lets say 450HPX12X(.55/60)= 49.5 lbs per min of air.
this isn't peak power flow but just that much air to get to that power number regardless of engine size or rpm.
i would expect that to get the most out of our engines is to use something like two 2.2L turbos placed somewhere like where the cats currently reside. the combined flow won't be great at low RPM, but that's what a positive displacement blower is for, right? then when you get to let's say 3grand RPM they'll come on and get things going. both these turbos are boost referenced by an internal wastegate to bypass exhaust past the turbine at say 8LBS. so combined at full steam a combined 16LBS would be getting to your I/Cs.
after doing some math that's quite a bit more complicated, i came up with for the 450HP figure you'll need 35PSIA pounds per square inch actual for the 3.8L engine. now subtract ambient of 14.7 from that figure and you have about 20 lbs of boost needed. now subtract all your bends in your pressured tract and intercoolers for 3 I/Cs and all the twists and bends to the order of about 6LBS of restriction. sooooo, 26LBS from the turbo at your boost guage to be in the ball park.
in a nutshell yes you can. twin internal wastegated turbos mounted as close to the heads as possible, but oversized a little to allow them to flow lots of air.