Any suggestions?
How would it effect performance and mpg?
Would it be louder than my stock?

 

i got striaghts with cats. i have a y pipe after the cat going into duals out the back, i like it, but i hear u loose alot of low end without the mufflers, so i am going to be installing a cheery bomb extreme SI/DO, sounds awesome and actually its almost as loud... hope that helps

 

IMO I would say get yourself a good muffler. Without backpressure you will lose some power on the low end. Also, of course running a straight pipe would be louder than stock. Most anything is louder than stock with the muffler and resonator on there.