The 336 has not been recalled for Gen4 9mm models, it has been "upgraded" to the 30274 version. There's nothing wrong with the old ejector, most Glocks including recent production Glocks eject just fine with it. If yours ejects fine with the 336, there's no need to change it. The new ejector was made to change ejection enough to compensate for another problem that causes erratic ejection by angling the case mouth of the spent casing higher so it can better clear the ejection port.
If yours ejects erratically, such as regular ejections back at your face, some straight up, and some even going left, you can upgrade to the 30274 ejector. You can find a local Glock Certified Armorer and ask them to install a Gen4 9mm trigger housing with 30274 ejector to replace the one with 336 ejector that's in your gun. The newest Gen4 9mm trigger housings, manufacturer part number 30275, have the 30274 ejector in them. If you don't have an Armorer in your area who can do that for you, you can call Glock, speak to the Warranty Service Department and explain the issue to them. You can arrange with them to send the gun back to them and they'll upgrade any parts to the latest versions, which would include upgrading the 336 ejector to the 30274 version for Gen4 9mm. You can ask for a prepaid shipping label but there's no guarantee that they'll give you one, if they don't it's pretty expensive to ship it back to them. You have to send it UPS or Fedex next day/overnight, you cannot send a firearm through USPS. You could ask a local FFL to ship it through USPS for you, they are allowed to ship firearms through USPS and it may be cheaper than sending it yourself through a parcel service.
If you feel comfortable installing the part yourself, so far three online retailers have been confirmed to have the Gen4 9mm trigger housing with 30274 ejector, the rest presumably still have the old version with 336. Those retailers are MidwayUSA.com, glockparts.com, and LoneWolfDist.com. One of my posts in this thread contains resources that show how to detail strip:
http://www.glockforum.com/forum/f10/g27-cases-bent-2342/
You may also need to try a new 9mm LCI extractor if you continue to experience erratic ejection with the new 30274 ejector installed.
As to the cause of the ejection problem, in some cases it's obviously caused by an out-of-spec extractor because replacing it fixes the problem. However in other cases like with my Gen3 G27, there seems to be another cause because replacing the extractor with one that works fine in another Glock makes no difference, only the new ejector shows any improvement in ejection. With my Gen3 G27, I believe the cut-out in the slide which holds the extractor was not positioned correctly.