2006 s40 sometimes won't start

[Ou2mame]

We have a t5 s40 with 34k on it and sometimes it won't start. It cranks strong, but just doesn't start. I replaced the fuel pressure sensor and the problem went away for a month and now it's back. It only happens on cold starts, and eventually it'll start.

There was no pem recall because it's installed under the back seat already. There are no codes, pending or otherwise now. But before I did the fps, it was showing a pending fault for low fuel pressure at start and the new fps seemed to have fixed it.

Anyone know where I should look next?