Again I would urge you to look at the standalone options, using a piggyback with ,more specifically, a Toyota ECU will leave you somewhat blind as to what is really going on. You'll end up just making almost random adjustments to get the desired results, where as with a standalone ECU you'll know the exact spark advance angle your setting and be able to calculate almost exactly how much fuel is being injected, in addition you'll be forced to learn how to tune the parts of the map such as cold start etc... that would otherwise be preprogrammed into the stock ECU.
Don't forget, if you buy a standalone ECU you can transfer it over to pretty much any engine you want to have a go at tuning. With a piggyback ECU you'll need to learn the characteristics of the OEM ECU your attempting to control, in some cases this can be very frustrating, time consuming and also get in the way of what your trying to learn. Think of a standalone ECU as an investment in your experience and education, not just an expensive part that your plugging into an old car.
There are several standalone ECU's on the market that are, price wise, very competitive with the EMU.
