Changing intake gasket on a 170, any tips?

If you have a vaccum leak, it will show up mostly at idle and not effect full throttle operation. So I doubt that you have a serious vacuum problem. Yes, there is a sealer call CopperKoat in a spray can. But, I would use a thin film of blue RTV silicon sealer gasket sealer.

When you say it hesitates at full throttle, do you mean it hesitates when you go from idle or a partly open throttle and then open the throttle quickly? Or, does it do this with the throttle full open for all of the time that you hold the htrottle full open?