if your going to skip the cat run only one muffler a flowmaster 80 series and then branch off of that with a Y pipe and do your own fitting from there.. There is enough room to put it there just run it wisely like not by fuel lines unless you shield them with some lineing other then that you should be safe. I ran duel out the back of my old 89 sse and it sounded good but I had a high flow cat I suggest you do the same. The 80 series flowmaster sounds awesome on the 3800. Make sure you dont run a to high diam. pipe so that you loose some power.