Hi everyone,
You know 2N3866 is capable for 5W maximum power dissipation and I assume it needs at least 500mW of input for that. If the mod4 design outputs around 200mW of power(am I correct?), a final 2N3866 stage as Q4 might give a blasting 1W or more of power. I would be rather interested in such a simple add-on modification because in your circuit 2n3866 won't be efficient(ie, input is only below 50mW). However it should work.
'2N3386' in your circuit is a JFET
I think 2N5109 has less maximum power dissipation than 2N3866. So the design is not good.
Another good modification I guess mode4(200mW)+2N4427(1W)+2N3866 = 5W plenty of power enough to be get traced by the police