I have heard of alot of purported failures with Melling hi vol pumps(SB's) so be sure & open it up & check clearances/clean it which should be done on any part & as mentioned there are alot of areas that can be ported. I personally dont think a pan can be sucked dry only that the pickup can become uncovered & on a high rpm eng I make sure the pickup/pan clearance is 1/8"-1/4". I think inadequate clearance there will starve an(high rpm) eng quicker than anything. I would think that the vol is going to max out at a certain PSI(maybe when the bypass psi is reached(or even before)) but I have spoken with some highly skilled eng builders who do swear by a hi vol.