problen with a tuned pipe is he MUST run the restrictor plates in the carb.
so likely a tuned pipe will not preform well, due to the limited fuel/air intake from the restrictor plate.
a few things. you can replace the stock crank bearings with a ceramic crank bearing. this will get you a faster spool up, more throttle response, and more top rpms.
ceramics can run from 40.00 for a pair of Team Fast Eddy ceramic crank bearings to 130.00 for a set of the Acer or Boca ceramic crank bearings. impo, the TFEs are great for the price. i have them in both my main motors with many gallons on them.
now heres some grey area. do you have to run a fully stock motor?
depends on the rules. but if you must run a completely stock topend the only other thing you can do it match the cases to the topend in the transfer port area. this will flow fuel better.
you can run a Stuffed crank with will also make for more throttle response and faster spool up.
if you can make mods to the motor, you can have the intake and exhaust port timeing adjusted to gain a bit of low end torque and top rpms.
or if you can have the topend fully modded, you can have all the transfer ports worked on. piston mods like dimpleing ect.. but you ll have to check your rules. as many of these things may be a disqualification if found to be using them.