Starting issues

Have a 1990 subaru legacy front wheel drive manuel transmission. It has aprox 165k miles. It has a hard time starting up on the first start. Requires excessive pumping of the gas pedal before it will start up. After the first initial startup the car will start up fine thereafter. I have already changed the spark plugs, spark plug wires, fuel filter, air filter, oil filter. I have also checked the fuel pump to see if it is pumping the fuel and that seems to be working fine. Any suggestions that you might have would be greatly appreciated! Thanks