There is some information here
that is more in terms of best mods, but some or most is applicable to a stock 93 with 140000 miles.
Things wear out. Things need attention and checking
First start with fluid levels. Coolant, oil, brake fluid. Power steering, clutch or trans fluid levels.
Then assess the condition of the fluids.
New oil and filter would be in order. VR1 works for me, and WIX filters.
Flush your heater core and new thermostat. stock is 195, but most use 180 or 160. My 93 runs too cold with 160, it has the 180 in it now.
Check brake pads, and flex hoses. Replace if worn.
Replace air filter and check for vacuum leaks around the manifold and TB
Clean or replace your O2 sensors. They affect almost every stage of your tune.
Replace your coil. Check your ICM while you have it out. Auto stores will test it for free.
While you have it there, get the store to test your battery and alternator function/condition. Replace what is bad.
Run some injector cleaner through the gas every few tanks. Cant hurt.
Change your spark plugs and any plug wires that look burned or worn. The plugs are a big chore, and hard to access, but with patience you will succeed.
Check your plugs for signs of fouling or dead wires.
That is a start.
Then go to shoebox's site here, and look at what you can do.
4th Gen LT1 F-Body Tech Aids