Exhaust cut out question

Im wanting to get an electric cut out for my 94 Z28 and im wondering what size i need to get. I have the stock pipe and i have heard there not a 2.5 but not a 3 inch. What would i need a 2.5 or a 3 in cut out??

3"
mine works great in my link is some videos of it working. Went from a best of 8.03 to 7.86. avg was 8.10's with open avg is 7.90's it works. I'm running header mid's, bolt in catr delete and flowmaster muff.

ok i think ikm going to go with DMH i looked them up and heard good things from them. Plus i can get it as a kit and cheaper than a lot others.

on the 96 and 97 models where would you weld-in the cutout (electric probably DMH as well) just because i believe i have post-cat o2's. i have heard near the rear axle? isn't that too close to the gas tank?

yeah i was going to put it right before the rear axle. I dont think it would be to clse to the gas tank. My buddy has one there and hasnt had a problem yet. And im not going to run it open all the time its more for when i go to car shows.

in my video you can see it. Mines mounted right up and under the passenger rear seat
I'll post some pix of installhttp://i16.photobucket.com/albums/b39/wyldcdn/electric%20cut%20out/Picture009.jpg
http://i16.photobucket.com/albums/b39/wyldcdn/electric%20cut%20out/Picture008.jpg

I'd look into throwing a turn down on at the end of the cut out. Trust me it makes a big difference in interior noise.

I also did a 3 1/2" QTP with a turu-down before the axle. Keeps the heat off the rear pan. The sound pressure wave can bounce back and cause increase in noise when @ WOT.