Need some advise please.

I had some problems with the original Pst controller as the engine would hung at around 27000 to 30000 RPM.
So the solution was to convert it to a Xicoy controller but it would seem the problem followed.

It ignites on the propane and starts to accelerate to 30K, then hung.

This 800 is new with only about 30minutes of run time.

One out of five starts is fine, with no problem.

Any suggestions?

Thanks in advance.
Marco