jvx800, For item 5, did you loosen all of the screws for the two rails that join the TBs together before tightening the TB's mounting bolts? If not you'll need to in order to prevent any vacuum leaks at the TB bases...worth checking the TB gasket also.
Is the engine backfiring when you blip the throttle? If so it's an indication of a lean mixture caused by a vacuum leak, a lack of fuel pressure, fuel volumn or both. The wrong map can also cause a lean condition, but as always rule out anything physical before changing the map or anything in the map.
On the other hand, if you smell gasoline the mixture is rich, which if severe enough can foul the spark plugs which will cause hesitation without any backfiring (usually).