boring it out to .090 over does nothing for power so no you dont need pipes for that reason. i would however get pipes because i like to go fast
it doesnt usually require rejetting because youre not changing the air/fuel flow through the motor by boring the jugs.if you put pipes on, you will need to rejet though.
and 24:1 is too rich. i mix 32:1 but some people go up to 50:1 and higher. just use a quality premix oil.