It's just when you strap the car on a dyno and plug the PCM into LT1 Edit or something like that. Run it on the dyno and the tuner tunes after each run to wring the most out of it. Generally better than a mail order tune, since the tuner has the car right there to tune to the individual package. It's also kind of fun to watch

 

would it affect my madz28 tune?! how much would it be?

 

It'd probably make more power being tuned on the dyno, Unless the tune you have is spot on. What kind of mods do you have?

 

The dyno tuner would go in and change parameters on your mad tune to specifically match your mods. I have read somewhere that alot of tuners "encrypt" their tunes so you have to go back to the original tuner. Jeff Creech at CAM knows his stuff.... they recently even flew him out to California to dyno tune a few cars.

 

Yeah he was up in NJ or somewhere around there last monday and tuesday doing some tuning I guess.