joe if you have never had the evap valve replaced on your 94 850, you should just replace it. we have have many problems with evap valves, even on the later model cars. the new one is a kit with a new valve,hose and wiring connector. easy to install. i had to replace it on my 94 850 turbo. when we get one in the shop with the 315 code. we check the hoses from the evap valve and cannistor. if they are ok and the valve looks original we replace it. never had one come back with the same problem.