[Pampered-Z]

With a dyno you are tuning under a more controlled enviroment, but you're tuning just the engine, not the entire drive train, shift points etc. Plus when with the engine in the car your tuning with all your equipement installed, intake, fuel system ect so you get a truer tune, you'll know more about potential problems like going lean etc. I'd perfer an in the car final tune.

As far as mail order, unless your setup is something out of the ordinary the tuner will likely already have a tune for you car. In my case, I used a base tune, and sent the tuner a dyno sheet from TTP's dyno and a scan of the car being driven for them to make changes, not as good as havng it done in person, but the changes seem fine. I'l sure there is more in the car though. but that was a few years ago.

Us LT1 guys do have a local option = JSP. I talked with his tuner an I was very happy with what he had to say, so my car will be heading there in the spring once the stroker motor is back in.