When I changed my fuel injectors, I installed a AFPR. I noticed I couldn't ever get it lower than around 45psi with the vacuum line off so I put my stock one back on and it reads 50psi with the line off. Why is this?

 

Mine read 48 PSI with stock regulator too. I thought this was a little high and I was searching thru the archives for stock fuel pressure for my 92 L98 and came up with 43.5 as being stock. If anyone knows for sure can you please post the correct STOCK PSI. My block learn readings are in the 116-118 range which is rich and before I go leaning things out too much Id like to know whats stock and whats too low before I run a risk of damage. If my 48 PSI and PLANT PROTECTION's 50 PSI is way high for stock regs, what would be some possible explanations for the high readings??

 

I thought the stock pressure for those years was 41, with vacuum, and 47 w/o.

 

look and make sure there are no pinches or kinks in your return line....if there are, you fuel pressure will go up

 

So far, Ive tested 4 TPI cars' fuel pressure. 3 were L98s, 2 88's, 1 89, and those 3 were all at approx 48 with no vacum. My Vert, on the other hand which is an lb9 was at around 38 PSI. Could never figure out why the others were so damn high.