I take it that he didn't even road test your bike after working on it. That's a shame and not a good sign at all of a good mechanic or dealership (stealership).
They wouldn't sell aftermarket parts for our bikes if they didn't work. It's not the mod's. It's a dealership and/or mechanic who doesn't know what he is doing. I think the carb needs work in the pilot jet, main and needle valve/shims.
Hopefully many more folks will comment and you can take these comments to the dealer for him to read.
*Your dealer/mechanic took the easy/lazy way out. Don't let them get away with it.