I was fighting a lean problem so I changed the fuel filter and decided to put a fuel pressure gauge on it. I remember when the car was on the old motor the fuel pressure was relatively constant meaning it only bounced on the gauge 1-2 psi and jumped like 5 psi with the vacuum line disconnected. Now it's bouncing between 40-45 at idle and 45-50 with the line disconnected. I can feel the pressure pulsing through the line on the gauge, I definately dont remember it doing this before. On a better note I fixed the lean condition and now it's really rich. I was thinking maybe because of the megasquirt it fires one bank at a time alternating that it's causing the bigger pressure fluctuation on the rail instead of the stock sequential.

 

Batch fire on a set of rails not designed for batch fire might cause that problem. What are you using for a fuel pressure regulator.

 

Just the stocker, when the car was on the dyno the AFR was smoothe so I dont want to change anything, but I put the fp gauge on it trying to find out the problem.