[MT-2500]

Go for a basic tune up with good AC delco plugs and see if you can find the misfire.
Clean MAF sensor.
Check fuel pressure.
Check cat back pressure.
The code 1141 is a evap solenoid or plug flow problem.
That may be caused by bad sensors or sensor reading or wiring to the pcm.
With a good engine capable scanner check BARO-IAT-ECT-TPS-and fuel gauge reading - AND PLUGE FLOW READINGS.
Also watch and check for any other codes.
For cat rattle check the shield around cat.
If the rattle is inside the cat is lose inside.
Usually caused by engine misfire or rich exhaust and or not running right.
Before working on/replacing the cat fix the engine running problems.
Also remember on the 97 the ign switch is a know problem area.
MT