I put 2530's on a rebuilt engine (still 2.6L, just with some forged internals, BNR32) and 1 bar would hit like a freight train at a tad over 4000rpm, making not much before hand. When I wound them up to 1.5 bar it only took an extra few hundred rpm to build the extra boost.
Put in some Tomei 260in/ex poncams, and the power seems to be more linear and comes on alot smoother, starting to build boost a bit after 2000rpm and on full boost (which is now 1.25 bar) by 4000rpm. The main difference the camshafts made was extra low down torque, which the car didnt have before, it was a complete gutless pig before 4000rpm.
-BUT- My turbos are second hand, but were rebuilt by HKS (I have receipts) in Japan before I bought them with 0kms on them after the rebuild. Wether they were rebuilt to standard 2530 spec or not, I couldnt say. Ive been told by a few people they arnt as responsive as 2530's should be, but pack a bit more top end punch.