In all my research, I have found the exact opposite - my findings have shown that the HX35 is one of the best, budget-friendly upgrades available for the 6.5L.
I am in the process of installing an HX35 on my 6.5L rebuild project. I will report back with findings when I am done.
Casey
1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter