Sump kit changes the fuel draw point....mainly to overcome effects from a fire hydrant returning too much fuel and messing with the stock draw point at lower tank levels.
Many times with installing a LP, the initial improvements felt afterwards are a result of the install (leaking parts removed), and/or the added positive pressure helps with various weak flex lines' bends that suck flat under vacuum and age.
When whatever fuel supply code goes away, the LP is proclaimed the solution...the same success results could've been resolved by finding the leaks/crimps/collapsed bends and replacing.
Which could prove more difficult to find and rule out, than the LP install itself.
1-14 thread filter bases are $25-$30 ea (in either top or side mount versions). A single FWS aux filter added pre-LP will greatly extend the life of the stock filter up front, by removing all the big particulates 1st and the added positive pressure will fully utilize the media of the stock filter (vacuum only, leaves unused voids in the media).
Also much easier to access the valve and drain any water collected.
If the additional primary and secondary filters @ the LP are doing their job, you should never have to change the stock filter again....keeping it as a backup for water protection.
Rated @ 50gph under vacuum (more with psi), it's not much of a restriction, as you'll never come close to burning 10gph.
After I swap out the 1st two filters, I check the vacuum pull (pump off) at the stock filter head (via an adapter at the bleed port) for any restriction that might be at that tertiary filter, and leave it be if it's not.
My current Racor filter installed there has had over 8k gallons of fuel ran thru it so far, still tests free and clear.
2007 LBZ 3500 LT3 DRW Crew Cab, Sulastics, Putnam XDR 15K, B&W 30K-Turnover GN+Companion, Ride-Rite Air...EFI'd by Rob
2008 LMM 3500WT DRW Crew Cab, 8 'Flat/GN, Workforce Alum Toolbox, Ride-Rite Air Use-ta Haves 2006-6.0 3500 WT DRW ExCab Flatbed, 2005-LLY 3500 LS DRW Crew Cab, 2002-LB7 3500 LS DRW Crew Cab I Live my life in such a way that when my feet hit the floor in the morning...Satan shudders & says "Oh shit, he's awake!"