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My NB8B has a GT2860RS turbo with .86 A/R turbine housing which goes great at high speeds but is asleep in DD mode. I have considered changing to a .64 A/R turbine housing but not sure if that would be that much better. Everything I have read says the GT2560 would be the best for my purposes with the least lag. The NB has a 3" exhaust, 710cc injectors, Haltech sport 1000 all the good gear.
My question for my fellow boost freaks is should I downsize to the GT2560 or change the exhaust housing to achieve fun lag free driving? By the way the car came with the GT2850RS and it has taken me a while to realise it is really meant for serious track work.

You should make boost at lower than cruise rpm with that turbo if the setup is correct. The 2560 is almost identical in every way that matters, id change the rear housing to a .64 and get someone who is competent to set it up for your needs.

Hey c-gazer, I have that turbo so I can comment. I also had a 2554 prior for comparison. The turbo size is not your issue, my 2860rs with .86 rear is alive and well above 2500rpm on anything from 15% throttle, and pulls cleanly in any gear anytime.

Cant tell you where to look next but if you post up all your supporting mods and if you have the dyno printouts it will show where to start. We did many combinations and heaps of full power runs on my car before we were satisfied we were getting the potential.