Heres a quote off
vortexbuick
Throttle Position Sensor Adjustment
The TPS sensor is used to tell the ECM how far open the throttle blade is open in order to assist in determining how much fuel should be injected at any given moment. This is not the only tool used. Air flow, engine load (LV8), etc. are also calculated and input for fuel control.
TPS adjustment is another area where folk lore has long persisted with no basis in fact. The sensor may be adjusted for idle voltage and wide open throttle voltage.
Let's start with wide open throttle settings.
Folk lore has long taught that some magic number such as 4.65 volts, or 4.80 volts is required from the TPS in order for the ECM to command Power Enrichment which provides the additional fuel required which the engine is under boost.
If you go Here and look at the chip dumps provided by Dave Huinker, and go down to line 1410 of the dump, you will see the factory commands power enrichment at 75% of TPS which is 3.75 volts.
Now, if you have Power Logger, or, Direct Scan, it shows when PE is invoked. You will notice that PE may come in at a much lower voltage such as 2.5v. This is because the TPS point is overridden by engine load (LV8) at part throttle in many cases.
So, is there any reason to have a wide open throttle tps setting greater than 3.75 v? There are a couple of reason. First, the factory programming shuts down the AC compressor at 4.0 volts so the compressor is not working when you go wide open throttle.
Secondly some chip makers specify a certain window for both the idle range and the wide open throttle range when using their programmable chips. These guidelines must be followed in order to correctly program their chips. Read the instructions that come with the chip and follow them in order to ensure proper function with these chips.
I normally set mine somewhere in the range of 4.2-4.8 v.
The main thing to understand is that performance does not change however you adjust the tps in the upper end.
If you have too high a wot tps voltage, then you will throw a code 21 (see trouble codes under troubleshooting section so it is best not to set the wot tps over 4.8 even if it will go higher.
Far more important, than worrying about why you only have 4.48 volts at wide open throttle, is to be sure that the throttle blade has moved as far as it can when you put the pedal to the floor. Look at the throttle blade lever when the pedal is pressed to the floor and see if it has gone all the way to the stop signifying that the blade is wide open.
If it is not all the way open, there are generally three possible reasons as to why it has not.
a)
The floor mat is restricting the pedal from traveling as far as it should
b) The throttle valve cable from the transmission has been adjusted too tightly and is not letting the the lever move as far as it should
c) The throttle cable has stretched and is not moving until the pedal has moved a short distance. If you get down in the floor board and look at the pedal bell crank where it connects to the cable, you can see the slack, if it exists, between the ball on the end of the cable and the bell crank. An easy fix for this problem is to put a small tie wrap around the cable between the ball and the bell crank to take up the slack. This will make the throttle blade begin to move as soon as the pedal moves and should restore full blade opening.
To determine the source of the problem, grab the throttle lever and move it by hand...
If it goes all the way and the blade is open, or nearly so...then it would appear to be a cable stretch problem.
If it goes all the way, but, the blade is substantially a distance from being wide open...removing some off the lever for more throw should help. I have never seen this problem but, I guess that anything is possible.
If it does not go all the way and make contact with the throttle body housing, then be sure there is nothing obstructing the pedal such as the mat. If there is not, then disconnect the tv cable and see if the lever will now move the rest of the way. If it does, then you know the problem is with the tv cable.
and if you have a TT chip heres another quote
TurboTweak
Chip Version 5.6 9/06/08
2
Sensor Readings and Adjustments
Fuel pressure: Start at 43psi (vacuum line off). Should drop about 5-8psi with line on. Adjust +/- 3-4psi
to where car runs the best.
TPS: Set the closed throttle TPS to .40-.46 volts.
Set the WOT position to 4.20-4.60 volts, do
not exceed 4.8 volts.
IAC: Car warmed up in Park, around 10-30.
Oxygen sensor: Car warmed up at idle, .750-.850 is typical.
At WOT on pump gas, .780-.850 is typical.
At WOT on race fuel or alcohol injection, .750-.800 is typical.
Take WOT O2 readings in 3rd gear for consistency. The reading will generally be higher in the
lower gears and drop some by the time you get to 3rd gear due to the O2 sensor heating up.
These readings are typical for Scanmaster, Directscan, and Turbolink. Other scantools may read
differently.