Outta breath...hmmm...and only during wide open throttle?
Did it occur after a few runs during idling? Is idle speed too high? How did the engine react after a WOT to idle? Is it responsive or it takes a while to get back to idling sound?

Can be a lotta problems aside from being too lean or too rich. Anyways, do the following...

- Check for temp after normal runs...not max throttle runs...too hot = engine too lean, cold = engine rich (what most people recommend if u dun have a temp meter is to spit on the engine block...your spit should sizzle and vaporize in 3 secs....too long, engine is too cold, too rich.... U also need to check the recommended optimum operating temp of your engine.

- Pinch the fuel line to cut engine....engine should rev up for about 3-5 secs b4 dying...too fast, engine is too lean....too long to cut, engine is too rich..

- Check fuel line for clogs
- Check needle for dirt accumulating
- Check your pipe for fitting, and air intake line from exhaust back to fuel tank.
- try changing glow plug...Might be Glow plug dying

This is the best we can help with typing... :L