2002 Cadillac Deville – 160K Miles

Engine Stumbles (pauses) uphill at highway speed, about every 5 minutes or so. I have replaced the air filter and fuel filter, added injector cleaner and 93 octane. Possible relevant codes include: P0741, P1860 & P1415. Not sure where to go next. Could be a vacuum leak or a bad sensor, but not sure how to chase either. I own two spare coil packs from a previous DeVille. Appreciate any thoughts.