I'm looking at a 99 5.7 with the possibility of buying. There was apparently a new engine about 15k ago. When the engine is up at revs oil pressure is fine. At low revs it drops to about 3 psi, dash lights up, etc.

Common causes for something like this? Sludged-up top end with pickup screen blockage? Failure to replace oil cooler with the engine change?

What think ye?

 

One cause for a drop like that, is worn Cam Bearings.