Picking another dealer isn't likely going to help. Search the forums on the ping/rattle in the engine and you'll see people from all over the United States (and I think a few from Canada) have been blown off by dealers. One poster mentioned a dealer was told by Toyota corporate to replace the heads. But that guy went MIA with no follow-up (lovely) from what I can tell.
At least 2 posters have been told (by dealer) that a 'fix' is coming in 2-3 months. One person posted that a day ago. Another person posted that...about 2-3 months ago. Yeah, Toyota is engaged in some serious smoke and mirrors B.S.
My theory - it's not something software will fix. There's probably a hardware component to it. Why? Most of the ping seems to come under light load for most people. Assume for a minute that you're coasting along at 45mph and get on the throttle a bit, at which time the ping kicks in. At coasting VVTi is busy doing it's best "Hey, I'm an EGR system, too!"-imitation. Once you get on the throttle lightly with a light load on the engine, VVTi is programmed to stop pretending to be something it's not and to alter it's behavior. This has been the case since 2005 with the Tacoma and the document about this is available on TIS under the 2005 "New Car Features" tab for the 2005 Tacoma.
So for several years, Tacomas played this game just fine (or so it seems, complaints seem to be most common in 2010 - 2013 models). Then something changed, and my bet is that something mechanical changed in a revised part for the VVTi system or something related to the VVTi system (oil control valves, the VVTi sensors, maybe a change in the oil passage that leads to the VVTi control valve).
So based on all the inputs the ECM takes, and all the commands it gives ("VVTi, stop slacking, be VVTi, not EGR! Spark plugs, fire earlier--no later--no earlier-no later--WAIT! Injectors, uhm...INJECT! Crank, what's your position? Cams, WTF are you? My paperwork says N-degrees, but you're at N+z degrees! WTFO?"), it can only balance the results of the hardware to a certain extent. Once a single part of the system is reporting in-spec, but functionally out of spec for the conditions, you get the ping.
Parts are going to have to get changed out. Maybe very expensive ones. You think Toyota wants to drop millions on that nonsense AGAIN? Do they really want Yet Another Black Eye, especially in something with a historical quality reputation like their smaller trucks? The whole reason MANY of us bought a 2nd gen Tacoma is because we came from 70's, 80's and 90's-era pre-Tacomas and 1st gen Tacomas. Sure they all had some issues, but There are THREE Toyota rigs in my family with >200,000 miles on the clock. An 84 pickup, an 83 pickup and a '98 4Runner (it's closer to 300k as I type, about 2000 miles shy of it). My 1st gen Tacoma (a '97) did 140k easy before I had to trade it (needed room, growing family). My 2004 again was solid (only had that one to 70k) until I had to once again trade up due to a growing family. Logical choice? Another Tacoma. Result? FAIL!
Toyota is going to lose reputation-based repeat sales en masse over something like that.
Also, FWIW - Toyota trucks are NOT the only ones with this problem. The Chrysler 3.6L Pentastar (Jeepers!) has issues beyond just the bad heads they have replaced. Some of them ping like this too. That engine also has a VVTi-type system playing EGR in the off hours. Nissan Frontiers? Some have the same problem. Folks with newer (2011+) Mazda CX-5's report PRECISELY the same type of noise under the same conditions in large #'s (no fix).
All the makers are trying to get every last bit of mechanical energy out of every last spritz of gasoline's chemical energy and they are pushing things to the ragged edge. In the process, they are updating and changing hardware (and software) to make this happen.
Sorry for the rant. I've been dealing with this since May of this year (16,400 on the truck today, actually -- problem first noticed around 10-11,000). 91 octane helps, but it's NOT a 'fix'.
As an experiment I put a tank of 87 in the truck yesterday (Shell, good stuff). The noises are worse and all over the power band (but still primarily in that 1500 rpm area). Prior to May 2013, I had only used Chevron, Shell or Valero 87 octane fuel. Nothing changed in May (on my part).
30 grand turd pile.