ecm swap

i know a 1995 3.8 ecm can replace a 3.4 ecm but are there any performance advantages to doing this

Welcome to the Forum Jason but a 3.8 ECM is not interchangable with a 3.4. What your probably thinking of is that 94 and 95 3.4 Ecm's are interchangable but the 95 3.8 won't work but even if there was another engine that used the same type PCM for a different engine you would have to completely reprogram it or the imput and commands would cause your car to run completely out of specs if it even ran at all.
John

found a web site that said they were i was un sure
thanks

No problem, Glad I could help.
John