Ron, I think I was one of the folks that steered you away from the BDP billet plenums based on my experience. I hope I didn't steer you wrong.
I ran into clearance issues with the TN kit, the drivers BDP plenum and the race cover S467. I had to clock the compressor housing so the discharge port was nearly vertical. It was a mother just to get the housing on without damaging the wheel. Maybe I have too much Ford Grey RTV between the plenum and cylinder heads...reducing clearance. I mean if Nate's done it on several trucks....it obviously works, that's an opinion I'd count on for sure.
But on my truck, it's tight even with the flat WOP plenums....I'll have to get a pic.
Swamps with the engine dyno and full instrumented test cell would know for sure, as I agree cylinder pressure testing would be very enlightening on this issue....but if you do the volumetric math on what this motor consumes for air at 3000 rpm...I just don't see how a raised design like the BDP plenums that contributes less than .5 cu ft of intake volume (between the two plenums) over the "flat" design can make a hoot worth caring about.
A change in IC piping from 3" to 3.5" diameter would add more volume to the intake system than a set of billet plenums. My math says a .030 over stock bore motor will add nearly 2 cu ft of intake volume over a stock bore just for the two holes at BDC after completion of the intake stroke.
I think some really big numbers for our ol' dino 7.3 have been made with the flat plenums. If they were starvin' the end holes on our motors....enough to twist/break stuff...wouldn't that be manifested in lower CPs for those holes...and therefore power numbers for trucks running those plenums?
I don't see how they'd hurt...for sure. Not arguing or looking to shove my opinion down your throat here...Just another fellas 2cents.
And IMO tuning/driving habits will play the largest role in keeping your motor alive no matter the inj/turbo combo. I think you're really gonna be pretty damn happy with that combo. Nate steered you right IMO if I remember your goals correctly.
Hell...I've got a set of billet plenums in the garage. You pay shipping to try 'em. If they fit then you buy 'em for a fair price. They aren't beat up or scratched (except a small rub on the drivers plenum). If the motor blows, I'll buy 'em back for what you paid.
Is that's all that's holding you up now?