After 450 fuel pump installed, car ran good for 2 weeks on E85. A/F was in the 14.7. Currently at idle, car is idling lean at over 21 on my wide band and will studder and die. I installed fuel pressure guage and it was over 75psi at idle. Did some googling and drilled out the siphon tube to 9/64, pressure has dropped to 60psi. Anyone had success lowering fuel pressure on single 450 with stock return or did you go with larger return or AFPR to lower fuel pressure?

 

Nvm...got it figured out

 

What was it ?

 

Replaced the stock fuel pressure regulator with an adjustable fuel pressure regulator.