Has been running well and strong w/ around 290K miles (in hindsight gas mileage may be down--I haven't replaced odo gear yet). No problems of late, other than tick tick noise and an rpm related rattle. I assumed ticking from probable exhaust manifold leak, and rattle from loose pre-heat hose and/or heat shield. Yesterday rattle sounded worse than usual, at more rpm frequencies. Performance OK until starting to climb mild hill at @50mph which car usually handles fine in 4th gear (5spd). Was having a bit of trouble so downshifted to 3rd. No power improvement. Turned around and headed back hoping to make it 3 miles. I kept rpms low and it ran OK. Can't remember exact noises, but did get a "dry" non-squeal sound, as well as a "whistle" type sound. All gages OK. No warning lights or unusual voltmeter action. My first choices are:
1. Plugged or broken cat--consistent with possible lower mpg, exhaust ticking, and excessive rpm rattling.
2. Locked pre-pump (90+ degree weather) or broken hose and failing main pump consistent with lower mpg, 1/4 tank of gas BUT never cut out, sputtered--just no power increase when throttle depressed.
3. What else????

Thanks.