Here'* what I've found out: the shop put 5w-30 in when it'* supposed to take 10w-30 but the guy I talked to said that shouldn't make any difference to pressure when at operating temp. He then suggested worn rod/main bearings (like the post above), or a bad sending unit.
I did some research and found out that overfilling the oil can cause aeration, and thus low pressure. I checked my dipstick again and it'* actually well above the hatched marks, could this be the culprit? Another cause could be a clogged oil filter (even though mine is only a month old) or a clogged oil pump. Here'* where I found this info... Troubleshoot Low Oil Pressure
Based on my symptoms: only low when engine is at temp, fine when rpms are anywhere above 1000, 5w-30 instead of 10w-30, the sudden manner in which the problem started happening, and no leaks accept for small ones in the valve cover gasket (which I will replace soon), what do you think the problem is???????
The first thing I'm going to do is drain some oil so it'* not over-filled, and if that doesn't change anything, buy a mechanical oil pressure gauge to see if it is actually low or just a bad sending unit.