Change your fuel filter in the fuel distributor, Change your fuel filter near the fuel pumps. If you have let your fuel tank run low then it's possible the filters have picked up some residual junk that resides in the bottom of the tank. If you let your tank almost run dry it only takes once for this gunk to fill up your filters.

If you have no cat and no O2 sensor by lifting up your passenger side carpet you will see the wiring meant for the O2 sensor. see photo. If nothings plugged into these then there is no cat. To install an O2 sensor improves the engines response and economy however the cost to do this may not be justified as it may require alteration of the header pipes to the first muffler.

The famous resistive plugs can have an effect on performance as they get older, - make sure you have the non resistive plugs in. If you can't get Bosch non resistive then NGK BP6ES are the equivalent.