Think the series he wants to race in, is ok without restrictor mate.

see here I told him to register on here... as you guys are the experts!

http://www.pistonheads.co.uk/gassing...+Torque+Limits

I think he would be better off fitting a bigger Turbo rather than ragging the current one.... you can run less boost for more power = less heat and less problems. Well thats my thoughts!