Front pipe section (motor to main chamber) available from Sammy Miller Products. Plated finish. They have had poor quality workmanship of the pipe joins (on the inside) in the past. Don't know if they have improved. I make my own header pipes and I'm sure any decent automotive exhaust workshop could also.
High performance and lightweight main section and end muffler both made from aluminium and well made- brand is WES. Available through
http://www.tytrials.co.uk/Both these are made for trials use so are tuned for power at low and mid RPM. They won't stop the motor revving out but if you want max HP, they are not what you would choose.
If you want to experiment, and don't worry, plenty of people have, you can get a chamber made to suit road use, but what about the other bits of the jigsaw? TY175 porting is same as DT175A,B,C,D but I think compression is lower and the carby on the TY is only 22mm. I remember gearing mine up when I was a kid to ride to work and it was spectacularly slow on the road.
One parts bike TY175 in my shed came with the sort of chamber that would suit what you want, but that bike has a DT175F motor, which is the later series motor that breathes much better than a TY175 B,C/DT175 A,B,C,D.
