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I am running a wh1c and 42mm HX30 on my 4BT and after getting many issues straightened out and a drive pressure gauge installed i can give a little insight.
I have the 30 gated to open at 40psi on the bench and the wh1c at 18psi this has resulted in ~ 42 psi at the manifold under WOT under 2,000 rpm with manifold psi climbing to
46 if I keep in it much beyond 2,000.
I have also installed a stop on the 30's wastegate that limits it's travel to .100" this has made the wh1c seem "happier" as the 30 and wh1c seemed to argue about who was gonna lead in the dance. My combo tends to run with between 3 and 10 psi drive over boost except when spooling, on the rare occasion that I'm on level ground for any length of time drive and boost are within 1-2 psi of each other at peak torque rpm's.
I am still doing a bit of fine tuning but it's real close now so it's taking more driving between adjustments, my last change was lowering the 30's gate to 38psi this shifted the load to the wh1c by ~ 5psi above 2,100rpm so next I'll lower the wh1c's gate to 16psi as I want to keep max manifold psi under 45psi.
All in all I'm really happy with it now runs it strong and will pull interstate grades at the speed limit with part throttle and EGT's of 1,050*, last weekend on a return trip from Phoenix
I got stuck behind slower traffic and ended up at 55mph on a good grade requiring a downshift into direct and with WOT I was able to get back to 75mph without much drama this doing this did see EGT's near 1,200* and more manifold PSI then I feel is safe for a Cummins head gasket hence needing to unload the wh1c a bit....there is a LOT going on between the two turbos and one little change affects much more that I would have thought before I started on this journey so now progress is pretty slow.
We all have our own path to the ideal tune so your results WILL vary but this should at leas help light the path for you, you have MUCH more control over your combo that I do...
GOOD LUCK!! I'll be following your results to see where it leads.
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