Originally Posted by Concillian
It is because of the dyno loading. Dyno loading is often not as high as street loading, so boost builds a little slower.
The tuner already posted in the thread mentioning it spools by 4k on the street, which is fairly normal for the typical size upgraded turbo for EJ205. I think you're in the right ballpark.
Dyno loading makes a lot of sense and I missed the comment from the tuner saying the it spools by 4k on the street. Thanks for the heads up!