Change the plug if you already haven't, just to eliminate an easy variable. Wouldn't hurt to put a new carb kit in if you haven't already. Those pumps can look good but give inconsistent results if they're beginning to harden. Cheap tune-up, even if it doesn't fix your problem you've at least eliminated that variable. I had a 026 Pro but some azzhole stole it so it's been a while since I've looked at one, does the air filter have a plastic choke stopper? If so, and if the spring is starting to weaken, the vacuum created by the carb can pull it almost shut or shut causing all sorts of mind-boggling issues. Wait until the next time it acts up, take the filter off, and run it in clean, open air and see if it changes anything.