I imagine is all using the datalogs. Obviously you can't get be so aggressive without having the car on a dyno but a street tune should be good enough for you to go out and beat on the car all your want you'll likely just be leaving some power on the table. I know not all setups are identical but for the most common ones I know there are generally known limits and best guesses at where ignition timing should be.

 

Pretty much spot on with this ^^. I had a custom tune done by E-Tunez and from reading this thread....it sounds like they both approach it the same way. Without being on a dyno, your not going to get "spot on" with the ignition, and for just a street tune...being a little conservative is best. May be leaving a little bit of power on the table, but I'd rather be safe than sorry.

 

Im definately looking into getting a E-Tune done next...I talked to xredjar about it for a bit and its going to my next move...I will keep this one in in mind. Thanks.