You'll find many posts declaring that
"the WIF system is flawed, doesn't work, worthless, and is a source for leaks."
Usually based on never having seen a warning pop up.
I've only seen it twice pop up, on two different trucks over the years. So, I CAN say it does work.
The sensor leads a rough life on many trucks. It gets yanked/stretched/pulled because it wasn't unplugged beforehand.
And it gets warped and molested by the wrong tools....when it only needs to be finger tight (seals with an O-ring), just like the filter itself.
Not too long ago, there was a Member who posted a save story.
He had left the stock filter in place, as the tertiary filter after a Lift Pump install with aux filters.
One day, "ding ding ding"
'Water in Fuel' warning popped up.
So much water from a bad tank of fuel, the LP FWS was overwhelmed....but the stock filter was still in place and did what it was designed to do.
There is no gain by removing it.
"But, it's one less filter to buy!"
If your two 'quality' filters @ the LP are doing their job, you don't need to change out the stock filter.
I'm currently @ about 60k miles on the Racor tertiary filter up front.
Checking pressure with fresh 2 filters, no LP power, it shows no restrictions.
When/if it does (or I get the warning),
I've got a new TP3018 here to try out.
It was On Sale for $27/free ship a while back, so I snagged one.
My 2 Baldwins at the LP, recently changed @ 15k miles, $28 for the pair.
There also have been more than just a few posts on a failed LP...one that claimed to be pass-thru, but wasn't. No way to prime if the stock head is deleted.