My Tracer has about 44k on it. When sitting at a stop light, idling, the car seems to run rough. Is a tune-up the place to start? The car was previously owned by an elderly lady (no kidding) so I'm not sure what she did as far as regular maintenance.

Are your rpm's low when sitting at a stop light and vehicle warmed up? You could check your TPS (Throttle position sensor) or maybe your egr is plugging up, or one of your plugs or wires could have gone bad, maybe the coil on one of the wires is bad. You really need to plug a code reader into the ECU and see if there is a code being thrown. And NO, all codes will not cause the engine light to come on.

Loss of power, but no mention of rough or inability to idle (including stalling). If those additional symptoms are part of the problem, check for a vacuum leak to the intake. Listen for hissing or sucking noises near air hoses. Look for loose, cracked, or broken air hose connections. Check PCV valve...Cheap to replace, could be sticking, then loosen after truck sitting with engine off. A vacuum leak will not give any light indications, and vehicle will seem to run normal when applying gas, but will want to stall or run rough (or want to stall) when at idle or sometimes when taking foot off gas when slowing down.

take it to an auto zone and have them read the code it sounds to me that you have a bad injector or two

simple test for a vacuum brake booster
star and run the engine at idle without applying the foot brake
if it gets worse when the foot brake is applied , it is a vacuum leak in the booster ( replace the booster )
otherwise check for failed vacuum hoses including under dash control lines , vacuum leak at the manifold or EGR unit

You've replaced too much. You could have a cracked coil. Start it up in the dark and watch for sparks under the hood.

Check your fuel vapor recovery system, your van has unusual set up, and the effect is RAW fuel gets purged, rather than vapor.
The dead giveaway test is does the issue happen on light acceleration? Does it stop if you let off the throttle? Can you accelerate harder and "get past" the issue?

Vacume leak or bad idle motor. With the car in park and running with the hood open listen for leaks moving your hand around the different hoses looking for a change in the sounds that you hear. The idel motor also makes the car idel up to 1500 RPM or so right at start-up then idel down, If it doesn;t the idel motor is likly. Check engine light is on when running? Test for codes, Follow code test charts don't skip any steps!.

probable vacuum leak query brake booster

lots of stuff in the fuel system can couse problem like pressure regulator, pressure switch,or relays. pump could be on way out though.

well spend some change and have a simple tune-up.  Plugs and filters and readjust the idle.