I'm going to save you some trouble and unneeded costs.
1. as mentioned, 94-96 cars get the optispark. You have the predecessor HEI (high energy ignition).
2. the HEI is an excellent system.
3. MSD boxes, among others, won't help you. You haven't done anything to your engine to demand hotter, or multiple, ignition sparks.
4. Also as perviously mentioned, spend the moey to refurb what you have: new coil, new cap & rotor, new wires. Also get a new sensor pickup for the INSIDE of the distributor. When you put it all back together, get the timing set to the stock spec.
5. You want more fuel economy? Upgrade the exhaust to the 92-93 9C1 ypipe and use a good low restriction aftermarket muffler. Leave the stock air filter but plumb the passenger side of the plastic "toaster" filter box for a second cold air feed. More cold air, slightly better air intake breathing, and a better exhaust, plus the ignition work will help you a LOT. IF you do these items, then you can probably benefit from advancing the base distributor timing by 2 to 4 degrees. It will help power and economy.
6. Have you taken the TBI off, taken it apart, cleaned it, and then rebuilt it with new gaskets? A GM TBI rebuilt kit would help.
7. Replace the fuel filter, check (or replace the air filter), change the oil and filter in the engine, remove and clean the PCV valve. Check the tire air pressure and make sure you have 35 psi in each one. Draining & cleaning the trans pan, adding a new tranny filter, and then refilling with fresh ATF can also help economical performance when the converter isn't locked up.
Most of the above are std maintenance items that are needed for optimum fuel economy. A few of them are cheap performance upgrades that will also help fuel economy.
There's probably a few more things besides these, but these are the basics. HTH. - Ken