For it to be THAT laggy id say theres somthing wrong rather than it being the turbo.

No way would just cut back blades etc make the bloody thing be 1000rpm worse in lag.

Even the ex housing would have to be drasticly bigger to be that much worse, and i doubt if its any bigger at all.

Id put my money on another problem, a unnoticed boost leak (intercooler?), wastegate not sealing properly, or some issue with cam timing or summat, as 5500rpm is REALLY bad even for a T4...