Adjustable fuel pressure regulator?

Guys, I just dropped in a new motor with LT4 hot cam roller rockers exc...and I'm using Accel 30# injectors and have added custom PCM tuning and an inline ATI fuel pump. The problem is that I think the car in running lean. I pulled the plugs this weekend and most of them were white. The car seems to run real good when its cold but starts running sluggish when it reaches normal operating temp. I'm sure this is because its in close loop when its cold therfore running richer, then leaning out when the car goes into open loop. Has anyone had this problem? should I be using an adjustable fuel pressure regulator to bring up the fuel pressure? If so, what should I set it at ?