so why do they ask bhp?

a t34.63 can make 400bhp just about, so potentially all esc cos bt, are insured for 400bhp, if my t4 is a 500bhp turbo? turbo size doesnt indicate power at all imo....

when its mapped i dont have to tell them the max bhp the turbo can make, i tell them what mine makes surely? and i cant answer that without a dyno run when its finished