Is it throwing a code?
Not really sure how you did the TPS reset properly without a "ecmspy cable" or Bluetooth module.
Also not sure how you came up with "its definitely been tuned" because the bike would barely idle and stall when given throttle. Yes, that COULD be the issue, but its no way "definite". Did the previous owner tell you they had it tuned? Usually they brag about it, since they paid good money to have it done, whether it was worth it or not.
Have you checked for leaks at the intake seals? You can do that while waiting for the cable to arrive. Leaks at the intake seals will cause what you're describing, as the bike seems to be misbehaving in high manifold vacuum conditions. Have you checked the IAC to make sure its functioning correctly?
Once the cable arrives, then do a TPS reset.
If you're looking to throw money at it, I'd recommend running a can of Seafoam through the tank. Will it help? Maybe. Probably not. But the iridium plugs probably wont help this either.
Free service manuals here: buellmods.com