94 Bonneville Misfire?

Hi all: 144k miles 3.8, ran fine until last week when going up slight incline at steady speed 45mph car had dead spot for 1 second. while driving that eve paid attention to issue and found under very easy gas load up highway hill at most speeds car misses. under heavy load car digs fine. ran in drive for 10 minutes then back to OD and seemed to go away for a while. Idles fine. Any thoughts? could it be as simple as plugs or wires? Ed