turbo advice/ turbo experts please.

Just got a new rollerbearing turbo for the b18ft, its a Garrett with a .86 rear and a 42 m27 comp housing.
I had been using a 200sx t28 with the .64 rear and 60front running 1.6ish bar. Can anyone advise me if this new turbo will be laggier due to the larger rear (engine limited to 6k) also will the smaller front housing flow enough air to keep up with the old one? I have a .64rear which I could put on if that would help, I also have a .60 front but don't know if it will swap over? Thanks in advance any help on this would be ace.;)