I've got a 1990 Corolla sedan, 5-speed manual, with a 4A-FE engine and just a shade under 160,000 miles. It used to run perfectly, but after an incredibly stupid act of filling up at Arco, it lost almost all power below about 3500rpm. I beat myself up about it, ran the tank down to about half, topped it off with premium and added a couple bottles (the small ones) of Lucas injector cleaner. I've since driven about 70 miles and it runs a little better--it runs perfect when cold but once it warms up it starts sputtering under stress and low revs, but now the power starts kicking it at about 2800rpm. I have no idea whether filling up at Arco and my car losing so much power was coincidental, but who knows?
I've got a few ideas of what could cause this, including a dirty fuel filter, dirty fuel injector, timing (most likely), and/or old spark plugs. The oil was changed just last week and I flushed out the engine about three weeks ago.
Other than that little quirk, my old Corolla's still in near-perfect shape.