Ive seen mainstream tune cars w/ e cutouts and open downpipes before i believe (dont take my word on that tho), just have some fans running to blow the exhaust gases outside, not a big deal.

Ive heard some 3 in exhaust turbo cars as well and they really arnt as loud as you would think. Shoot ive seen a civic that has 3 in. all the way back w/ no muffler and its really not that loud. Of course, when you get on it, its gonna get kinda loud no matter what, thats expected, but it would be even louder w/ the e-cutout. Plus with the e-cutout, u will lose power during normal driving so id say just go w/ the 3in.