Can anyone tell me why my long term fuel trim is at -25 idling and to temp.
02 Monte Carlo SS 3.8

 

Most likely a vacuum leak. 25 is the maximum the PCM will allow the MAF to compensate for.

 

The car has a pretty bad surge around 2500 rpms with light pressure on the throttle. Had mileage had dropped from 28 to 23. The fuel trim is the only odd thing i can see. No codes at all.

 

Pretty typical symptoms for a vacuum leak. Listen for hissing all around the engine compartment, especially around the upper intake manifold and associated vacuum lines and connections. If you don't find anything obvious, try spraying some carburetor cleaner around those areas and listen for changes in rpms.
Also try unplugging the electrical connector from the MAF and listen for the difference.

How many miles on the car?
What maintenance has been done on the engine?
Has the upper intake manifold been replaced?

Here's a video I find very helpful to understanding and interpreting fuel trims: