Engine stumbles

The first thing to do is have the trouble codes pulled. Advance Auto and Auto Zone do this for free. See what comes from that as it will lead you towards the source of the problem.

Then I would test the fuel pressure and make sure it is correct. Advance and Auto Zone have fuel pressure test gauges on a loaner basis. The test port is on the fuel rail. The fuel pressure should come up when ignition turned to, "ON" position. The test specs say to test for pressure in this state. It should be 47-50 PSI.
I gave you a diagram of the test gauge port location and what hookup should look like. You als have the fuel pressure release procedure.

The engine compression speca are;
Normal 185 PSI
Minimum 139 PSI
Maximum Variance 14 PSI

Check the following items as sources of hesitation and lack of power;

Ignition wores for corrosion and proper connection.
Vacuum leaks.
Idle Air Control Motor, IAC.
Mass Air Pressure sensor, MAP
Throttle Position Sensor and connection, TPS.
Ignition and coil circuit.
Crankshaft Position Sensor, CPS.
Camshaft Position Sensor, CMP.
Coolant Temperature Sensor.
Fuel injectors.
Air inlet blockage or restriction.
Exhaust blockage or restiction.
Oxygen sensor, (If the MPG is higher than normal).

I have included a Sensor Location Diagram that has the position of the above components.

As far as the speedometer, check the Vehicle Speed Snesor, also on diagram.

It is unusual that the Tachometer is erratic as well as the speedometer. The tach picks up its signal of the Camshaft Position Sensor. It may be that a ground is bad that the instruments share.
I am giving you the ground locations in a diagram for the instruments. Check them for corrosion and/or correct connection.
The locations for the ground in the list are started with a capital, "G" followed by a number. Connectors are a captial, "B" followed by a number.

Let me know how everything goes and if you need anything else.

Ignition and coil circuit is in the list. The coil can be tested before purchasing it.
Any information needed for specs can be retrieved whenever needed.
However, this is usually an explanation for the irratic Tach, but the Tach picks up its signal from the Camshaft Position Sensor. So, get the codes pulled first as it is free and can shed light on the situation without going through the entire list as it will in the least eliminate possibilities.