swapping ECU's

Lotsa times when i read about engine swaps, most people wire the old engine up to their stock ECU....and ive also read that it dampens performance. So heres my question(s):

Whats the cons of swapping ECU's? How difficult is it? Why dont more people do it?

Lotsa times when i read about engine swaps, most people wire the old engine up to their stock ECU....and ive also read that it dampens performance. So heres my question(s):

Whats the cons of swapping ECU's? How difficult is it? Why dont more people do it?
The only time Ihave heard of someone keepin their stock ECU is when they have a Si/EX, and then they get them chipped to spec to run the new motor. Swapping in a C1 and keeping a DX ECU is retarded. Of course it is going to hender performance, as in the case of say a non vtec 1.5L ECU trying to run a DOHC vtec with completely different fuel and timing maps.

The only time Ihave heard of someone keepin their stock ECU is when they have a Si/EX, and then they get them chipped to spec to run the new motor. Swapping in a C1 and keeping a DX ECU is retarded. Of course it is going to hender performance, as in the case of say a non vtec 1.5L ECU trying to run a DOHC vtec with completely different fuel and timing maps.

meh ive probably been misinformed...So where are the difficulties in swapping an ecu?

meh ive probably been misinformed...So where are the difficulties in swapping an ecu?
just have to make sure all the wires get connected at both ends:sunglasse conversion harnesses make it easy and you dont end up with random wires to hide:iceslolanlike mine

Well you question and you text don't make sense together, first your talking about using stock ECUs on swapped motor, then you want to know if it is difficult to change an ECU, um no it takes about two minutes. If you're changing OBD's you need a conversion harness, easy, easy, easy.

Sorry if my posts seemed jambled...but yes my question has been answered thanks.