I have a 99 gt with 175000 miles on it and every so often when I go out to start it all it does is just turn over and wont start, if I give it gas it starts but I have to keep my foot on the gas for a while then it will idle. I am either thinking fuel pressure regulator or fuel pump. When I get home from work today im gonna rent a fuel pressure tester. What should the pressure be? If it is the fuel pump can I buy just the pump and screen or do I have to buy the whole assembly? Thanks