No one said it would not work, many have used it, problem is for it to not put the engine at risk one has to lower the CR to 18:1, the Holsett has to be modified to fit up, requires inter-cooling to use the high temp air charge fully & is a used turbo until rebuilt.
The ATT is a direct bolt on NEW turbo no lowering of CR required, IC or WMI can be used if you need it, IMO that it is only required if heavy towing or operating in the upper performance envelope, it increases mpg so over time it pays for itself.
If you have fab skills, are willing to live with lowered CR & willing to do the work and access to the Holsett go for it.
ATT vs Holsett in a race, who knows what the result would be, in a tow I'm pretty confident the ATT will hold it's own or surpass the Holsett, thus far with exception of Buddy no one has pushed the performance envelope of what a ATT will do most of us just tow with it or sport on the street with it a little, but ATT is no slouch to be sure.
I'm doing some OBD-II peaking & tweaking stuff myself; it is too soon to know what the end result will be, Buddy has some things going on his rig, couple of others doing some things also, the ATT is relatively new to the 6.5, Holsett has been used with some success, but not enough to warrant the extra work IMO.
What you won't do is direct bolt on a Holsett like you can a ATT , especially on a old engine and have it last boost regulation is not a problem for ATT.
BOV if you think it needs that costs $$$ so more to think about,
Bottom line and a lot of thought went into this, the ATT cost for new is comparable to total cost for Joe Average 6.5 guy to retrofit a used Holsett onto the 6.5,
A number of 6.5 guys do run the Holsett it just requires more work than most are willing to do.
So no crap/smack talking at all, is ATT the best maybe maybe not, is it an affordable solution that gives more power, and anyone with basic wrenching skills can manage most definitely.
and this is not to disparage what you have done in the past, when you start talking blow off valves on a Diesel it's a dead give away, no throttle plate slamming shut on a Diesel to worry how much air going to the engine. This crops up when gasser turbo guys 1st delve into turbo Diesel, which is same in some respects but also different.
