i'm trying to see how much fuel presure i'm running but i don't know what reading to go off of. It show's 2 different reading off of my fuel gauge:

1. when the car is at idle it reads 30 psi.

2. when i engage the throttle it shooots up to 40 psi.

how much psi should i be running on my h22 swap, i was told 40psi what do you guys think?

 

40 psi should be fine, you should check with vaccum line to fpr disconnected, that will show you fuel pressure the car will see wot.

 

The FPR is always trying to keep your fuel pressure 40psi above whatever pressure's in your manifold. So when you're idling your manifold has 20" of vacuum, which is about -10psi.

 

so you guys are saying that my current fuel pressure is 30psi, i should be reading it when it is in idle.

 

boost your pressure to 43 psi. you can still do it when the car on idle. just take of the vaccum hose that connects to the FPR and it will read the reading like it is at full throttle.

 

Yeah, disconnect the vacuum line from the FPR, plug it so it's not a vacuum leak, & leave the nipple of the FPR open. Now measure your fuel pressure. That's a more reliable measure since your manifold vacuum might be fluctuating.