Good Day!
Many moons ago, someone (can't remember who, might have been Banks) used to sell a kit for the 6.2's. It consisted of (I think) a non-restrictive air intake from the radiator support area, a thingy that attached inside the top if the IM to smooth the airflow, & exhaust manifold adapters. IMHO the good Dr. has got it right. "Swanger Air" the intake & toss the unbelievably restrictive factory exhaust-manifold-to-pipe adapters & you might actually be able to measure the improvement. The problem is: where do you get the exhaust adapters? Maybe the good Dr. will give you drawings of his & maybe he won't (or can't).
I trust grape on this one for sure, unless someone has the magic formula(s).
Blessings!
82 6.2NA K15 4X4 pickup, 4spd man w/ OD, 335K+ "In Rust We Trust" (parked)
95 6.5TD 2500 4X4 pickup, Gear Vendors Aux. OD, > ¼ million miles - gone
95 6.5TD 1500 4X4 3/4T Suburban, Kennedy exhaust, > ¼ million miles
93 6.5TD 3500 4X4 1T crew cab LB pickup, 230k miles