To change you can go to a very responsive turbo like a 550BB etc. Or you can swap the cores in ur swappers and just upgrade the rest of the car to take full advantage of those. SZ reccommends sport700 turbos as the next upgrade because they spool similar to stock with breather mods but I feel this is only with head work. I would want custom tubular manis with borg warner efr turbos and custom down pipes but hey thatz just me. But if you decide to take that route look up qfab on facebook.
"torque gets you off the line...& hp gets you over the line." - TTKeeper