swaping ecu's any problems?

hey i was looking at some civics ek.. i saw one that has a b16a2 engine in it and it has a CTR ecu from japan in it.. from what i heard from the owner and he also has the original ecu that came with the engine. are there any problems with using the CTR ecu??? and are there any problem when putting the original ecu that came iwth the engine back on for instant to pass emissions or something???

oh and the CTR ecu is supposebly partially tuned.. not for track but for some daily driving. but not hte original..

are there any problems with using the original ecu again afterwords?


and how about a civic with a b18C5 97' .. if it has a n1 ecu and the original ecu is gone.. can you get a used ecu and put it on to use instead of the n1 because the n1 would kill gas and cause emissions problems.

can i just plug in some ecu and it should work??