If you car is fairly stock, you will not gain much. In fact, you should probably spend money elsewhere. The more mods you make, the more a chip is valuable. Some years respond better to a chip as well. Like a fox body chip wont do much for you, and they are sometimes finiky. A 96-newer allows more control, but you need to "need" the changes that are being made. On the newer cars yet, the first changes are usually to disable downstream o2's for catless h/x pipes, and to turn off limiters. Cars that have turbo(s) or blowers will pretty much need a chip and then to be tuned on the dyno to get everything right on the air/fuel. If you took a supercharger kit, installed it, and used their chip, for example....and then had a chip custom burned for you on the dyno, for YOUR car specifically, you should see some good gains in HP. We generally order the kits without the generic chip, so we can provide a custom chip for that very reason. As for N/A applications, there are still alot of things that are involved in tuning, but timing and fuel adjustments are the keys. Tuning on a dyno will ensure you have the correct A/F. Price range varies by the shop. When do you need to be re-tuned? Its not like a tune-up, it only needs to be done when there is a problem, or something in the system has changed.