ls1944

I just dropped an 02 LS1 into my Porsche 944 and I just lost oil pressure. When I first fired up the engine last week I had the same problem and I tracked it down to a pinhole in my Milodon pickup tube, I installed a new pickup and the problem went away. I've been driving the car for a week or so and put on about 500 miles with no problems. Yesterday when I was at a stop light I noticed some lifter noise and the pressure dropped to about 20 psi. I got on the freeway and it went up to 40 ish then after about 5 minutes it jumped back up to 60-70psi. It drove fine and there was no noise. As soon as I got home and stopped in the driveway it dropped down to nothing and the lifters got really noisey. I let it sit for a few hours and fired it back up, it idled for about 10 sec. and the oil pressure would not go back up. Do you guys think it could be the pump? I'm leaning towards another pickup issue myself since there was plenty of pressure at high RPM's.