I need some help here. My daily driver is a 94 4x4 Suburban with a TBI 454. I changed the fuel pump and filter the week before christmas(old pump died) and ever since, the thing runs rich at idle and stumbles. The problem is especially bad when it's warmed up and you shut it off and restart it. It'll surge when in gear and stopped too. It seems to be worse at night when there's more electrical load with lights and all.