I cheated and did not do this mod myself. I had the local Tuffy shop do the install for me. They charged me $100 to bolt it on. Pics are down at the bottom of this page. Most people recommend that you weld the thing on. I only had mine bolted on in case I ever need to take it off for some reason. I will recommend you get some good clamps, the ones that come with the Borla suck! They tried to use them - and they broke. Get some good 3" clamps to use instead. I did have the tips welded - the driver-side pipe bends right before the tip - and we couldn't get the clamp on good. I had 1 side only of the clamp welded - so i can remove the tip if needed.
Hey I watched - it was worth the $100 bucks to sit and watch some one with a lift and an air gun do this install. BUT - if i had to do it again, i'd do it myself.
As for the plates... the borla comes with 4 plates (closed, 1/3 open, 2/3 open, wide open). these plates go in the pipe before the muffler. This allows you to regulate how much exhaust goes through the muffler and the amount of noise your exhaust will make. Most people find the 2/3 open plate gives the most horse power on the dyno. Wide open is best for 1/4 mile. The wider the plate - the less amount of backpressure - hence less low-end torque but more top-end HP. This is why the wide-open plate is best for racing. I originally had the 1/3 open plate in. SOTP power seemed about the same. I wanted more sound so I now run the 2/3 open plate. Sounds good - and yes there is a noticable SOTP loss of low-end torque. Since I don't race - this is fine with me - it helps save the tires during normal driving :-)
Here are some pics of the catback...
Borla - under pipes
Borla - under muffler
Borla - rear
Borla - rear 2
Stock - muffler
Stock - muffler side
Stock - side
Stock - rear