One thing to watch with the GMS32 is that the low-speed needle has quite an effect on the hi-speed mixture. It's easy to get the situation where you've leaned out the low-end so much that no matter how much you open the main valve, it can't get enough fuel at full throttle.

Try richening up the low-end so that there's a gap between the low-speed and the spraybar when at full throttle, then tune the top end. Once that's sorted you can start playing with the idle-needle to get a good idle.

On the GMS32 I'm running a tuned pipe on I have had to deliberately set the low end needle quite rich in order to get anough fuel-flow at full throttle.