1955 Chevy LS1

Hi guys,

I need your help!!!

The car is a 1955 Chevy with a 1999 LS-1 in it. It always has ran great and now it is running rough at idle and has low power.

I have an Auto Enginuty scanner on my laptop and scanned the engine and it is not kicking out any codes.

The MAF was replaced and it did not effect the problem.

I vacuum tested the MAP sensor and it appears to read the correct volts reference vacuum.

Do you have any suggestions as to where I should continue looking with my scanner???

Here is what I know so far:

So with my scanner all of the bar graphs are "green" except the Barometric Pressure volts and pressure.

Barometric Pressure Volts are steady at 4.78 volts regardless if the engine is running or not and the min/max ranges listed on the software are supposed to be between 0.00 to 4.98.

Barometric Pressure was also steady at 14.61 PSI and the min/max range is supposed to be 1.45 to 15.14 PSI.

The Manifold Absolute Pressure bar graph moves as expected and indicates around 15 PSI at idle and the software states the min/max should be between 0 to 37 PSI.

The four O2 sensors seem to be working correctly and the pattern of each seems to move in the same range as each of the other three.

I have some O2 sensors out of a 2007 Chevy Tahoe I can swap out with my existing sensors however I do not know if they are the same units.

Does anyone have any suggestions of what I should do???

Bill