ECU / PCM Upgrade-ReFlash...?

[north42g]

2002 MP-5. 98,500 miles. The Engine/Power-train is completely stock. I have heard of re-flashing the PCM / ECU to gain Horsepower and/or performance.
What does this re-flash actually do?
Does it alter the timing? Does it dump more fuel? What Is really happening when this re-flash is completed?
I have also heard of replacing the PCM / ECU with one from a different car all together, for instance the mazdaSpeed3, is that correct? What are the benefits of this? What are the draw backs, if any?
All input on the subject is appreciated...I am very interested in installing on of these performance upgrades.

 

[azuelke]

All info can be found here: http://www.mazdas247.com/forum/showthread.php?123746537-FS-MP3-ECU-150-shipping

Everybody that has gotten one will agree it is well worth the price. In order to do this thought, you must have 2.0 5 speed, or it won't work.

 

[north42g]

As a matter of fact...I do have a 2.o manual trans 5 speed. Thanks for the info!
BTW....Why couldn't I just go down to the Mazda Dealership and buy an ECU from them? Is the price the only difference here?

 

[bazooka joe]

i think the price would kill you! i see them on ebay every once and a while

 

[Droopy]

Look for an 2001 MP3 ecu... Thats the one that people use

 

[north42g]

i think the price would kill you! i see them on ebay every once and a while

I grews up in eastie! (Brandywine then to the heights!) Now I'm out here in no-where ville!