My son and I have been able to make over 30 hp on an FMF exhaust.
Other exhaust systems might make a few more here or there, but I can assure you, the FMF will not not hold you back. 30 hp in a Blaster is a lot of fun.
It is more about the head, ports and jetting than the pipe.
Get a rechambered head, widen your exhaust port window and jet it properly.
She will fly (if the basics are solid).