My Echo SRM-266 string trimmer is about 2.5 years old and has developed a problem. It is easy to start and will idle indefinitely but will not accelerate (bogs down) until it has warmed up for a couple of minutes. Then it works fine for as long as I want to use it, typically 2 - 3 hours at a time. I've rebuilt the carb and the exhaust spark screen is clean but nothing I have tried eliminates the problem. Is there an ignition module problem that can cause this? It's still under warranty but the Echo repair places are backed up for weeks and I need to finish weed whacking for the year so I can't afford the delay of taking it in right now.