I have 2 RedMax EBZ-8001 backpack blowers that we are trying to resurrect. Both units will start but do not run anywhere near full strength; they both bog down really bad as they attempt to throttle up so we think whatever the problem is, it is affecting both units. Here is a list of things that have been replaced on each unit: new short-block motor, new carb, new fuel lines, new fuel filter, new spark plug. Both are unaffected when running with muffler off and also gas tank cap off. We are awaiting a new insulator & gasket and think that there is not much else that is not brand new on these blowers. We have several of these blowers that work great, so we even tried taking the carb off one of these good working blowers and swapping with a brand new one on a bogging blower, and it did not affect the bogging blower. Finally, we took one of these bogging blowers to a local repair shop. They looked at it and said it was a timing issue. After they tried to re-set the timing, the same problem persists and that made no difference. They gave up on it & said they'd just be throwing parts at it (which is what we have already done!) ANY IDEAS/SUGGESTIONS??