1st thing I'd probably do would be to put a fuel pressure gauge on it before a cold start. See how quickly fuel pressure comes up to spec (~40 psi). While you have the gauge hooked up, make sure pressure stays in spec (28-40 psi) while "getting back into the throttle."
For more details on performing a fuel pressure test, see the fuel pressure mini-diary thread (in the Under the Hood forum, I believe).