Thinking about making my own cat back system with some smaller after market mufflers, will i loose power or gain power ? any ideas what mufflers to go with to do this ?

Eisenmann is one of my top favorites... I suggest going with them!

You can do it but I am not sure which mufflers to use. I personally had 2.5" midpipes put in. Just remember to put a H in the pipes and it needs to be in the section 2 area.

Thinking about making my own cat back system with some smaller after market mufflers, will i loose power or gain power ? any ideas what mufflers to go with to do this ?

Yes, you will very likely loose a little power, you will gain nice tunes and may shed some weight.