The lower intake gasket. You need to have the pumps cam lobe on base circle before installing. Loosen the bolts a little at a time alternating between the two. Replace the oil and filter if the pump was leaking fuel. Reset the fuel trims with a scanner.

“Caution: Alternately hand-tighten the fuel pump bolts one turn at a time until the pump is fully seated. Trying to draw down the pump without even side-to-side tightening may result in pump plunger damage.”