The tuners run $350-400, not exactly a reasonable price. It's not that the computer can't keep up with the mods, it's just that once you start changing injectors and MAF meters all too often we end up lying to the computer which results in misinformation. Maybe we mean the same thing. Anyway, the tuner also requires that you have to be able to manipulate the tables accurately. If you aren't comfortable with that then a custom chip is probably the way to go. They run about the same price with a dyno tune.
You can't borrow a tuner either, it has to be permanently attached to the EEC. Once you remove it, all modifications to the operating program go with it.