the thought came to me that since the previous owner did some stuff to the car before he traded it in, maybe he put in a performance PCM. Is there any way to find out if it is stock or not? Would there be a lable, stamp, or something differentiating it from a OEM PCM?

Not necessarily.

if you go about 30mph and floor it. You should feel a skip shift though. It will snap your neck as it goes from 3rd gear to 1st. That means it's aftermarket.

AS well most AM-PCMs have a cool down period after the car is turned off. Does your fan run for a minute ?
There may also me a sticker on the PCM identifying it.

Get the car up to temp (drive it around for a while).
Turn the ignition off and remove the key.

Fan on = reprogrammed
Fan off = stock oem

Yeah. skip shift and fans are a good way to identify it (btw... the fans might not stay on if the engine isn't over a certain temperature when you shut it off, even if it is good and warm... depends on the programming). As well as checking if theres a label on the PCM.

If you have a scanner, it's possible to check the VIN. There are several people out there running with non matching VIN's.... If the VIN's do match up, you'll have to do some field testing as talked about below.

There are a couple of speed determiners. The downshift to 1st at 35MPH. Stock PCM will only go BACK to 2nd at 35MPH.

If you have room to open her up, you can put the car in 3 and get 'er up to 85-90MPH. If she shifts to 3rd in that range, it's stock. If she waits until 95MPH, it's aftermarket. And of course the all knowing speed limiter. Stock PCM limits the GTP to 126MPH. You will be able to go well beyond that if your car is running right with an aftermarket PCM.

a GT is limited to 108ish isnt it?

DOH!!

You have a GT.... Yes, stock PCM is limited to 108. And your downshifting to 1st will be in a different range due to shorter gears. Not sure what speed you should test the 3-1 at.

Speaking of the limitation of 108 on GT's.....I have the 97 GT and I wanted to remove the governor....but will this be safe? What I am trying to say is that was the governor installed for engine safety purposes or was it installed because of speed limitations. I was thinking speed because the Monte has no governor from when I and my friend raced. He got up to about 140 and again I dropped at 107, not 108.... .....thoughts? Thank you all for your help..-Jon

Which Motored Monte? Any mods?

Only way to up the speed limiter is a reprogrammed PCM. The reason for the speed limiter is due to speed rating on tires. If you up the speed limiter and plan on running those speeds get tires that are designed for those speeds.

Limiters are set at 108 and 126. But due to speedo error what you see on the speedo will very a couple mph or two or three.