This thread is a chronicle of the things I did to de-restrict my fully restricted DT125R, If you are on 'L' plates this is something you can do after you pass your full bike test and not before.
Well stage one has been sorted, I took off the exhaust and found one of those tube within a tube things in there so out came the dremel again, heres some before and afters, the last pic shows just how severe this thing is compared to the one i found in my DT175MX
Comparison with the restriction i removed from my DT175MX