How your water pressure can be made better depends entirely on what type of system you have and unless you are willing to post more really this topic is going nowhere. Do you expect people to guess??
What do you mean by a two way valve? A two way valve is just a normal valve where water can flow in either direction.
i assume that by 'two way valve' you mean some kind of manually operated diverter valve that sends the pumped water either to the bath or shower and not both simultaneously.
not aware that such a system exists and if not then probably for good reason. it IS possible to set up your system with a pump to service more than one appliance but it needs to be done with care - best to get a pro in to take a look.