95 5.9 46rh 260k.
Erratic oil pressure guage reading under load, just noticed this the other day. On highway cruise control under 2000rpm it's fine, but if I take off cruise then its erratic like it's about to drop pressure. Could it be the guage or do I need to go ahead and throw a high volume oil pump?

Probably electrical issue, but instead of throwing parts in it randomly, get/loan mechanical gauge and see what actual pressure is. Gauge that has long enough hose that you can hook it up so it's readable while driving.