Dave,

It could be that the low speed is set too rich if you're getting that delay. I had that same problem with my Evo engine, along with lots of other problems. I called Horizon up and they said to send it in (it was still within the warranty period). A week later I had a shiny brand new Evo on my doorstep. I slapped it in my plane and haven't had any problems with it since.

Might be worth a call to Horizon...