Well let me start by saying I’ve been front to back since installing new fuel pump mind you oem pump only has 32,000 miles on it ( original) but here’s back story. 1991 3000GT vr4 bought new by prior owner in Texas USA car was drove for first five years after that maybe twice a year afterwards now short version car didn’t have alot of miles but the sitting killed some items fuel pump cam seals and start drive without waming up engine hence #2 rod bearing mucking up . I have rebuilt whole engine and did all bushes front and rear do to age while waiting on engine and heads being milled and rebuilt. So my delimma began with at guage before entering fuel rail engine at idle.29psi. So replaced fp with new 355lpg figured bigger better right no not right when shut car off pressure dropped to zero in 30 seconds. Then as of last week I finally thought about pump stock pumps have built in non return valve this is to hold pressure for cold starts ,installed the 355 walbro and yes I came to this knowledge it doesn’t have an anti back flow valve in pump .I ordered 255lph walbro it has anti flow back valve now my idle is 42psi at idle and have let the car set for 3 days as of today guage showed 40psi and car cranked right up the 255walbro is good to 500bhp and cold starts are great . So if you look at replacement fuel pumps make sure it has any flow back valve before installing it or when car is cold might take up to tree turns of key to start and all the time fouling plugs .. Hope this helps someone else in this dilemma..