I'm throwing headers on and then sending my PCM in to PCMforless. I bought the car used from a new car dealer and have no history of the car, but know from the hard shifts, down shift points, and upshift points that it must have been programmed before with something. Plus the lower gears and speedo being accurate. I'm not sure if there's any internal engine work, just the obvious external mods. I want to send my PCM in and not exchange it, because I'm very happy with the way it shifts and hold's gears. I don't want that part messed with. The question I have is when he get's my PCM can he tell what's been changed from stock programming and if the car has been retarding timing and if anything else doesn't seem to be alright when it's been running. The car feels very strong and seems to be running perfect, but I have never drove a car this fast to know any better. All I know is it runs very rich at WOT, actually is stronger at 3/4 throttle vs. WOT. Thanks

 

You've asked a two-part question. Anyone who can program the PCM will be able to look at it and see that (or if) the program has been revised from stock. No problem.

As to the stored data.... in general - no. The PCM does not log any data. It stores the array of "long term fuel corrections".... what it learns about A/F mixture in closed loop at part throttle/low loads; it stores the "learned idle position" for the IAC motor... the throttle bypass valve that controls idle speed; and it stores DTC (trouble) codes. But the second you pull the power off the PCM to remove it from the car, it will lose all that stored data.

To have someone do a "mail order" tune, it helps to provide them with a dyno pull with wide-band O2 sensor data, or at least a data log of a WOT pass, showing as many of the engines vital control sensor readings as possible, and some low load/part throttle driving conditions, so they can see if the closed loop tuning is correct. You will also need to tell them the type of injectors you have and the flow rating, if those are not stock. The flow constant and the offsets may have been correctly programmed previously, or they might not be. Things like non-vacuum compensated fuel pressure would also be useful to the tuner.