ISIS T25/T28 replacement turbo v. S15 T28. Input appreciated!

[TAP240]

As the title states, I'm looking for some input on the ISIS T25/T28 turbo replacement option from enjuku (yes I searched and didn't find the results I was looking for). A buddy of mine works for enjuku so he introduced me to this option today. Long story short my S15 T28 is done for, so I took it off the car today and need a turbo ASAP! My current set up is (well was) and SR20det with an S15 T28 turbo..it's tuned with the AEM tru boost, I can change from stock tune, to a 12lb tune, to a 17lb tune; a/f is right where it needs to be in each tune (10.8-11.0 on a hot day and goes to 11.2-11.5 when it cools down at night). The car made 325whp on the dyno with the T28 on 17lbs. My question is, would I still be able to change between tunes and still have the ability to boost at 17lbs with the ISIS replacement turbo (I'll more than likely get the tubular manifold and I'll have to get the o2 housing as well), or will I have to keep the car at the 12lb tune or stock tune? I would imagine that the spool won't be as quick as the S15 turbo, but I don't mind sacrificing a few hundred rpm for the turbo spool. I'm also curious if my dyno numbers will see a drastic difference.
Any insight would be greatly appreciated!