Correct me if I'm wrong but i thought the waste gate being open was a bad thing? I thought the less the gate opened the better?
PSJ and others have nailed it already, but to expound further.
The turbine side of the turbo has a limitations to what it can flow, just like the compressor side of the turbo does.
Relatively smaller turbos (<66mm comp inducer), have lower rotating mass, so they spool at lower rpms. BUT...they usually are paired with "smaller" turbine wheels/turbine housings, that flow less as well. So you'll see most of the smaller S362/366 type setups will be "1:1" up to about 30-35 psi, then the motor will be making more exhaust mass flow then the turbine wheel/housing can accomodate. Back pressure rises, turbo speed goes outside it's intended range, compressor is no longer very efficient...bad stuff.
Relatively larger turbos (>71 mm comp inducer)
usually have larger turbine wheel/housing assemblies, that can flow a larger amount of exhaust mass. Because they are larger, they have greater rotating mass, and take more exhaust mass energy/rpm to "spool". You'll see some of the larger fellas are "1:1" as high as 45-50+ psi. All is awesome with the larger turbos...except spool.... in some cases.
So what folks have started to do is run "smaller" turbos that spool quick, but then to keep the turbo alive, and keep BP vs Boost relationships in line, they run a mount with a WG, that is set to "dump" excess drive pressure/exhaust mass energy to your down pipe once you've made your upper rpm power/boost goals.
On talk of nozzle size..and injector spool....turbos are driven by exhaust mass energy. So talk of larger nozzles being able to spool x larger turbo, is really speaking to adding more heat to the exhaust than a smaller injector would at a given rpm range. This is a poor plan IMHO...you'll end up with a hot/smokey truck, and with a turbo that lights like a light switch. Fun, certainly. Cool to bomb around town/beach, tow, and DD. Not for most.
The injector size/type/nozzle and turbo all need to be purchased as a system, and with thought tied to each other....because...well that's what they are on your motor. If you do it piecemeal, without tying A to B to C...well, you'll end up not where you need to be. I'm not saying you need to dump $5k at once....I am recomending you make a plan, where the injector size/type/nozzle and turbo are all thought of together towards a specific goal/use for the truck.
What DP tuner is offering is a custom designed, fit to your platform turbo by one of the best turbo brains in the business. Those line of turbos, already have the math "built in" for the 7.3 platform. All you have to do, is just pick your power goal and go. The turbos are all journal bearing, so when you need to do a CHRA (center housing rotating assembly) rebuild a million miles from now, it's very economical. The BB CHRA often times make replacement of the entire turbo more economical.
There are obviously other "box turbo" choices that have proven to work as well. The GTX4294R is a very well regarded turbo for your goals, but pricey. It is a water cooled CHRA, so that bodes well for longevity of the turbo. It does add a small piece of complexity to the install. The S467 FMW turbo has caught on lately, it's a big burly S400 turbo, that's tough as nails, and comes alive on my truck around 1800-1900 rpm, and I've pushed to the low 50s psi wise. PSJ's setup sounds like a fun truck too. You can definitely do well with a off the shelf turbo.
But if I'm spending your money, I'd rock a Bell turbo. A close second would be the GTX if your budget would permit, and if not, then a S467 FMW. Jake @ Irate sells those turbos too.
I don't have any experience with the Holset or Turbonetics stuff. I know there's folks running those turbos and are happy as well.
A great thing to do pre-purchase would be to ride in a truck with that injector/turbo combo, to ensure it's gonna do all you want it to, so that after you plunk your hard earned cash......you're happy!
Hope this helps, didn't mean to hash out stuff you already were tracking on, if that's the case.
Turbo 50 lb brain dudes...if I'm pointing this guy in the wrong direction, or talking out my arse on any of the stuff above.....fix it:swordfight:
Don't want to steer anyone wrong!