Some more info i have found from some forums about this turbo( This is on a evo 2l though):
"Hi guys-- Here's my take on the ATP 3071, fwiw. It does indeed spool up just like the 3037 (also .63)/custom tubular manifold set up I had on our One Lap car. However, it does this with a *stock cat* and not the test pipe that I run. All things equal, I suspect it to have 700-8000rpm spool up advantage to the GT3037 which is really quite good. Also, on our dyno, boost lag tends to be exaggerated due to the way the engine loads up. Well, not really exaggerated... but it comes close to representing the boost lag you feel on the street when you load it up in 3rd gear. If tested with a much slower ramp-up rate (simulating the first 5 or so seconds of a Dynojet pull where the big rollers are slowly getting up to speed), boost response with drop by another 400-600rpm which is where I suspect ATP is getting their sloop up claims. As such, their claim is perfectly valid and the difference in spool up that we are seeing is based mostly on differences in testing methods. Nothing to create a controversy about, IMHO To give you an idea of how different loads and different gears can effect spool up, look at this: In 4th gear, lugging from a low RPM, the big GT35 on my car can reach 20psi by 4500rpm. In 3rd, it takes until just under 5000rpm. In 2nd, it takes until past 5500rpm. So spool up numbers, by themselves, don't explain the whole picture-- especially when dealing with bigger turbos."