I had an interesting visit with my infiniti Service Manager today. When asked if upgrading the stock ECU in my 03 G coupe he informed me that I should purchase a "piggy-back" unit. Apparetnly, some of his customers are installing upgraded/re-mapped that are seperate from the on-board ECU and are removable and undectable?????? Can anyone offer any light on this subject??

Greddy Emanage Ultimate is one of the better piggyback units available. Yes, you could remove it, and if done carefully, might be undetectible that it was on there. However adding the EMU is not an easy job, and really not something you want to remove once it is installed. Not to be rude, but if you don't know what a piggyback unit is, you will be way over your head trying to install it yourself. You will need to pay a shop to install it, and dyno tune it. One of the reasons it can be so difficult is that the f/a maps on the EMU need to be uploaded once the unit is put in place. It comes with a baseline map, that will start the car, but to gain performance, you will need to add some additional maps, and tweak those (while on a dyno) to make everthing worthwhile.

The piggy-back ECUs are mainly for boost apps. They allow you to tweak your timing so you don't have detonation from running FI. If you have an aftermarket intake and exhaust, you might be able to squeeze a few HP from the unit.