I want to do a engine swap on my 94 Nissan Sentra XE and I don't know if I need a new ECU. I want to put an SE-R engine into it. And I don't know what else I need to do the swap? So if you can give me some advice I'd appreciate it. :confused:

You will have to change the ECU and I believe the wiring harness as well.

do a search, the button is in the upper right, many people have asked before, here is a quick list:

Engine (obvious)
sensors ( if it doesn't come with them)
wiring harness
ECU
Axles
Some motor mounts will/may be different on different models
Tranny
Correct flywheel/clutch
Tune up items are highly suggested "while your in there"
downpipe/get your exaust fixed to work with it (not sure how different, if at all the B13's are)

Lots more than that, a healthy supply of nuts and bolts will help too :-P

Chris