If I remove this should I plug both vacuum hoses. seperatly or join them together?
untill I remove them from their source

 

If you are driving the car, yes, plug them, as the white is teed to the distributor vacuum advance capsule. The black connects to a port on the bottom of the right throttle body and would create a (small) vacuum leak. If you connect them together your vacuum advance will be in operation at idle and probably not driving.

 

Thanks for the info RGK. My 40 year old one
is leaking much like most of the ones on ebay
so not sure what to do about it.

 

Having just been through the distributor and advance system, I noted that with those hoses plugged you will likely get a little spark knock on throttle tip in after coasting; the purpose of the valve is to “dump” the vacuum advance under those conditions. How much and how bad depends on engine temperature and fuel octane, I noticed it after a 20 mile warm up at freeway speeds, and it got progressively worse the hotter the engine was.