02 oil pressure light

[illinois_stroker_444]

hey guys, i need some suggestions on where to start with this i'll try to be short....turbo bit the dust, put on garret 38r(bad@$$), while i was in there put new hpop o-rings, valve cover gaskets, all o-rings in turbo pedistal, now when my truck gets warmed up oil press. gauge drops like a rock check gages light comes on. still runs like normal, cant hear any noise difference in motor when gage does this. so i put new sensor in, didnt fix it. short of buying an oil press. gage, i'm lost. also...#5 cylinder took care of any metal shavings my turbo sent in so its at 345 pounds of compression where as the others all 390-410. doesnt smoke either. please help!!

[NCHornet]

If the CEL is on I would start by scanning the codes and see what they tell you.