You need to timing light to properly check timing at idle and also at 3000 rpm.
Th problems you now report are possibly the carb balance or the timing. You can find a cheap timing light at Harbor Freight, if you don't have one, and the shorting rods will help with the carb balance.
There are also other better methods but they also cost more for carb balance. You can find mention of an Inmates product in Vendors about the Harmonizer. This tool is the latest and greatest solution to the balance problem. It doesn't sound very cheap but actually there are more expensive solutions.
See how you do with the shorting rods.