My 93 cougar like sputters when running. no power, and idles real hard. what could this be?

I'm guessing fuel pump is going. Check for 40 PSI pressure with fuel pressure gauge. Check in engine comaprtment.
Section 10-01: Fuel Tank, Filters, Lines and Electric Fuel Pump 1995 Thunderbird, Cougar Workshop Manual
DESCRIPTION AND OPERATION Fuel Pump, Electric The electric fuel pump:

• Is part of the fuel pump module.
• Is located in an internal reservoir in the polyethylene fuel tank (9002) .
• Is mounted with its inlet at the bottom of the reservoir.
• Is designed to increase satisfactory pump operation during extreme vehicle maneuvers and steep climbs with low fuel levels.
• The high-pressure fuel pump module on the 3.8L SFI and 4.6L-2V engines can supply 60 liters (15.9 gal) of fuel per hour at a working pressure of 269.0 kPa (39 psi).
• The fuel pump module on the 3.8L SC SFI engine can supply 125 liters (29.0 gal) at the same rate and pressure.
• The fuel pump module has an internal check valve to maintain pressure in the system after the engine is shut down.
• The fuel pump module also has an internal release valve to provide protection from too much pressure if fuel flow becomes clogged in the fuel filter (9155) , the fuel line is damaged, or other factors.
• Overpressure is limited to 850 kPa (123 psi) and reduced fuel flow will result if the pressure relief valve is activated.
• The fuel pump module is protected at its inlet by a nylon fuel filter element (9365) which filters contaminants which could plug or damage fuel pump components.
• The fuel filter element simultaneously allows passage of small quantities of water which may accumulate within the tank reservoir.
• The electrical system has a fuel pump control relay in the powertrain control module (PCM) (12A650) which provides power to the fuel pump module through an inertia fuel shutoff switch (IFS switch) (9341) that is normally closed.
• The electrical system provides power to the fuel pump module through two relays:
  • Fuel pump power relay.
  • PCM power relay.

• When the ignition switch (11572) is OFF, contacts of both relays are open.
• When the ignition switch is first turned to RUN, the PCM power relay energizes and closes its contacts.
• Power is sent to the fuel pump relay and a timing device in the powertrain control module .
• The fuel pump module runs through the contacts of the fuel pump relay.
• If ignition switch is not turned to START, the timing device in the powertrain control module will open ground Circuit 57 after about a second.
• Opening the ground circuit deenergizes the fuel pump relay, which opens its contacts and de-energizes the fuel pump.
• The circuitry provides pre-pressurization of the fuel system.
• When the ignition switch is turned to START, the powertrain control module operates the fuel pump relay to provide fuel while cranking.
• After the engine starts and the ignition switch is ON, power to the fuel pump module is again supplied through the fuel pump relay. The powertrain control module senses engine speed and shuts the fuel pump module OFF by opening the ground circuit to the fuel pump relay when the engine stops or is below 120 rpm.

Good Evening, In the grand scheme of things it could be a lot of different things, however the first thing I would say is try unplugging the mass air flow sensor there by the air filter and see if it picks up and runs better. It is possible to take it out and try cleaning with some brakekleen to knock the dust and carbon off. See if that helps improve let me know and we can go from there.