I know your frustration, if you go to the Echo website ande look up the pb-210e model unless you use the serial number of the unit you may get the wrong carb part numbers, The pb-210 and the pb-210e and the final model pb-210ep ( I think?) were made from early 1980s till 2007 June.
Every one of the carbs used for nearly 30 years was the WAT carb line... there were "california emission" (CARB act) pb-210ep's that were made for the last six months of 2007 that use that junk other carb. with the needle anti-tamper caps/ limit. The first time I saw those on the blowers I thought someone had swapped it off a old junk ryobie or something. 99.95% of all echo blowers still running (pb-210 family ) use the WAT carb.
If you plan on keeping the blower, change the carb. or order one of the newer junk kits and keep it on hand . Few shops stock it, and anytime the blower does not run right... the carb needs to be taken apart...( ether to adjust the needle or clean) just because the adjustment on the needles is so limited..
Check your fuel lines for small cracks, replace your fuel filter, look at your intake rubber boot for cracks (between carb/air cleaner housing), if no luck, try to adjust your needle lever higher (to allow longer needle open time on the metering diaphram and give you a richer mixture).