In the past few weeks I have been researching this issue hard. And what I have found is that its a common problem on these vehicles. I know people have written this up before, but I wanted to consolidate my findings so we can stop wasting money on components that are not bad.
The information is spread out. I want to bring it all into one thread. If anyone else has input for this, add it on.
Ultimately it would appear my issue was my fuel pump ECU and I fixed this by bypassing the fuel ECU.
Ok first is the MAF. People seem to replace this first and it seems like a good percentage of the time, this is not the issue.
Here is the FSM page for the MAF. You will need a multi-meter that reads resistance and DC volts for this check and some insulation piercing leads.
Do your quick resistance check from THA-E2 and see if the resistance is close to whatever the ambient temperature may be. Obviously if there is an open circuit or some other wild reading, your meter is probably bad. Chances are, resistance will be in spec.
Put the connector back on, turn the key to the on position (Do not start), apply your insulation piercing leads to the red connector on your meter. Peel back the rubber boot so you can see the 5 wires.
With the volume air flow meter plugged in and back probing, check for a 5.0 volt reference to the volume air flow meter on the Blue/Red wire with the key ON. Check the volume air flow meter grounds on the two Brown wires - look for 0.05 volts or less. Place your black lead on a good ground point to check for voltage.
Now start the car. Check the volume air flow meter output voltage on the Yellow/Green wire - look for 2.0 to 4.0 volts with the engine running. Make sure the output voltage is NOT 0.0 volts or 5.0 volts.
If this all checks out, you have just eliminated your MAF as being bad.
Another possible culprit of hesitation is the idle air control valve. Located right on the front of the plenum you have a few options for checking it.
You will have to carefully remove the plug wire tray to get to this.
Undo the 2 bolts holding it to the plenum. Disconnect the cooling lines. Disconnect the connector and pull it out.
Do your resistance checks and if you feel real adventurous, connect your battery leads to it and stroke the valve to verify operation.
You can go one step further and remove the 3 phillips screws holding the stepper motor assembly to the mounting body. Now the full valve is exposed along with the motor armature. Spin it in and out a few times to verify it moves smooth. Clean it up, lube it up and reinstall. OF course replace if any readings are out of spec.
Throttle position sensor checks
The TPS sensor is the inner most sensor in the picture. Mine has Trac, your might not. Tools you need to check this. A multi meter. A set of feeler gauges, 10mm socket to remove the throttle body cover for access to the stop screw.
And I found this on here. I have to give props to Cure, who suggested this. It works great.
This is a power connector out of a computer. Shave down one side of the connector and it will fit into the TPS sensor perfectly. Now you have a nice place to stick your leads and take your readings.
Follow this procedure exactly. I found that setting my gauge to continuity so it made a tone, Insert your 0.40 mm (0.016 in.) feeler gauge, between the throttle stop screw and stop lever. Loosen the screws and turn slowly till continuity disappears, than go back you want it as close as possible. When I did this, all the other readings were right. Might take some trial and error
So if all of these things check out you have did a pretty good job of eliminating your MAF, your IAC valve and your TPS as culprits of hesitation. I will detail the fuel pump ECU checks next. Gotta tend to the children.