What diameter pipe should i run for my half bridged 13b with an HX40 with on/off throttle response in mind?

so what i have now is a half bridged 13b and a hx40 going into the RX3 to be a dedicated hill climb car ( race car number 4 lol )

the hx40 is a divided 19cm^2 exhaust housing

obviously i am looking for mid range torque and power held through most of the top end.

I bought 2' schedule 10 304ss weld els and started thinking maybe i went too big. (the weld els ID is over 2')

And if indeed i went too big would it be ideal to start with the 2' sch 10 and taper down to any advised ID?

 

That's what we build all of our manifolds out of. The 2"pipe is fine for what you are going to be doing