Blockage in the rocker line is unfortunately common, but it only restricts flow to the rockers. Your gauge probably won't show anything.
Low pressure is:
1. reduced output (excessive end play in the pump, very (very!) small leak in the pick-up
2. oil too thin (10, 5W20)
3. bad relief valve spring (relief opens too soon)
4. loose bearing clearance
Using straight 30 isn't a good idea unless the air temperature is always high, takes too long to get to the bearings.
If you have 10-15 at idle, and 30 or more cruising with 20 or 10W30 you're probably safe for now, but don't beat on it.
