Hey, I have a 2002 Legacy L wagon 160k, automatic. Im getting a p1518 code. The car is driving horribly. It starts fine but when you gas it, it cuts out like the fuel is shutting off. Sometimes once I start it, it immediately stalls. Almost killed myself pulling out into traffic and it stalled. First I checked the battery post's and the positive side was heavy corroded. As I was cleaning it I noticed the post connector on the positive wires had a broken spot, so I replaced the connector. I removed the starter and cleaned all the connections there also. Hooked everything back up and its still driving like crap and cutting out. I figured it must be the ECU so I replaced it and it's still driving like crap and still giving the p1518. Anyone seen anything like this before? 

I also replaced the front O2 sensor

http://www.ultimatesubaru.org/forum/topic/81077-cel-p1518-starter-switch-circuit-low-input/

I think the code will go away if you figure out the power issue.

 

I would check fuel pressure first. Some years around that time had an issue with a cap on the fuel pump assembly. The cap fatigues and breaks and bleeds fuel pressure back into the tank.

Pics here: http://www.ultimatesubaru.org/forum/topic/130624-2000-outback-fuel-pump-assembly-metal-cap-is-broken/

That thread also has a link to a replacement part.

Subarus option is to replace the entire sender assembly.