Echo pb-250ln runs really well and then just dies, normally will not restart.

I have an Echo pb-250ln leaf blower which someone left by the curb. Taking it home I was able to figure out that the exhaust screen was almost completely clogged with carbon. I left the screen and other exhaust plates off and got it to run well. This little thing seems to blow just as strong or stronger then a Husqvarna backpack blower I have and is much more convenient, I love it. 
 
For a while now it has been giving me problems, it will run well, with much power and for a good while but it will quit before I want it to. It will just die and normally will not restart. So I used it this morning intermittently and it would run strong and then when I was almost done needing it died as if you turned the kill switch on. Sometimes this happens with a loud pop and then kill switch dead. Normally trying to restart it will just kind of backfire and not start.
 
Just went out after it had sat for more than an hour and it started right up and ran like a champ.
 
What I find confusing is that it will normally run long and strong and then just give up. I recently put the exhaust parts back on but the power was greatly reduced so I took those parts off again.
 
I have fiddled around with the carb, new parts new aftermarket carb, new hoses but it still torments me.
 
Any ideas where the problem might lie would be appreciated.