I have heard so much about replacing the ECU i don't know what to beleive anymore so i was wondering...
1. Is it good?
2. Is it leagal?
3. How do you do it? i.e. What is a "piggyback" and can you replace it yourself and do you have to re program it?

So confused...

 

its not really worth it unless you have some extensive mods done, it can give you a few horses, but your monet would be better spent elsewhere to start. some changes are leagal, like a full motor swap can use the intended computer no problem, but most states have individual laws on those kinds of things. and as for piggybacks, its a computer that intercepts the signals going to the stock ECU, and changing them slightly, tricking the ECU into putting more or less fuel into the engine at the desired time, it can do a bunch of other tasks too, but thats the main idea. its hard to get any power out of a piggyback without a dyno, but its possible with a wideband O2 sensor and AF gauge.

 

when youget a swap it comes with an ecu right?

 

yeah.