Vibration on hard acceleration

[Precious]

I have noticed a vibration, almost an up and down feeling on hard acceleration on my 98 RSTD. Is this normal?

Air pressure is good both on both suspension and tires.

Front end is tight with no wobble. 

On smooth acceleration there's no vibration. 

[RDawson]

Have the carbs been synched? It will cause a vibration under load if they’re unequal. 

[Precious]

Thank you. I haven't done that.  Will try to find someone who can.